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Hawkes K. Life history impacts on infancy and the evolution of human social cognition. Front Psychol 2023; 14:1197378. [PMID: 38023007 PMCID: PMC10666779 DOI: 10.3389/fpsyg.2023.1197378] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 10/06/2023] [Indexed: 12/01/2023] Open
Abstract
Greater longevity, slower maturation and shorter birth intervals are life history features that distinguish humans from the other living members of our hominid family, the great apes. Theory and evidence synthesized here suggest the evolution of those features can explain both our bigger brains and our cooperative sociality. I rely on Sarah Hrdy's hypothesis that survival challenges for ancestral infants propelled the evolution of distinctly human socioemotional appetites and Barbara Finlay and colleagues' findings that mammalian brain size is determined by developmental duration. Similar responsiveness to varying developmental contexts in chimpanzee and human one-year-olds suggests similar infant responsiveness in our nearest common ancestor. Those ancestral infants likely began to acquire solid food while still nursing and fed themselves at weaning as chimpanzees and other great apes do now. When human ancestors colonized habitats lacking foods that infants could handle, dependents' survival became contingent on subsidies. Competition to engage subsidizers selected for capacities and tendencies to enlist and maintain social connections during the early wiring of expanding infant brains with lifelong consequences that Hrdy labeled "emotionally modern" social cognition.
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Affiliation(s)
- Kristen Hawkes
- Department of Anthropology, College of Social and Behavioral Science, University of Utah, Salt Lake City, UT, United States
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2
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Afonso JD, Barros S, Albert I. The Sense of Belonging in the Context of Migration: Development and Trajectories Regarding Portuguese Migrants in Luxembourg. Integr Psychol Behav Sci 2023; 57:518-546. [PMID: 36085348 DOI: 10.1007/s12124-022-09721-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/28/2022] [Indexed: 11/05/2022]
Abstract
The sense of belonging can be defined as a highly subjective and dynamic feeling of acceptance, inclusion, and connectedness to a specific contextual entity. Perceiving belongingness to others is positively related to psychological well-being, happiness, or higher self-esteem. The present contribution examined how the sense of belonging to spatial, social, and cultural entities evolves over the migration process of Portuguese first-generation migrants and their second-generation offspring residing in Luxembourg. The current study drew on the qualitative content analysis of ten semi-structured interviews, carried out with ten Portuguese migrant family dyads (one parent and one adult child per dyad). The results affirmed that the sense of belonging showed to be a complex and multi-faceted concept and highly shaped by specific contexts. The initially unfamiliar Luxembourgish context became a familiar setting and even a "home" over time. While the older generation presented noticeable belongingness to Luxembourg as a homeland, their affiliation to the Luxembourgish community and culture remained rather low. Simultaneously, they preserved a high connectedness to the Portuguese culture as well as to fellow Portuguese migrants living in the Grand Duchy. The younger generation expressed a much more pronounced attachment to Luxembourg, since they perceived belongingness to the Luxembourgish spatial, social, and (multi)cultural milieu. In addition to this, a certain affiliation to the Portuguese culture and language could be discerned. Although some factors, which might have contributed to this evolution, could be identified in the present study, one can assume that there are significantly more that have not been addressed yet.
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Affiliation(s)
- Joyce D Afonso
- Faculty of Humanities, Education and Social Sciences, Université du Luxembourg, Esch/Alzette, Luxembourg
| | - Stephanie Barros
- Faculty of Humanities, Education and Social Sciences, Université du Luxembourg, Esch/Alzette, Luxembourg
| | - Isabelle Albert
- Faculty of Humanities, Education and Social Sciences, Université du Luxembourg, Esch/Alzette, Luxembourg.
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3
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Lee R, Chu CYC. Theoretical perspectives on reproductive aging. Front Ecol Evol 2023. [DOI: 10.3389/fevo.2022.934732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Age patterns of female reproduction vary widely among iteroparous animal species with determinate growth. Often fertility declines with age, but in other cases, it may be flat or rise across age. Sometimes fertility ceases altogether, leaving a substantial post-reproductive life span. In this article, we discuss theories that may provide some insights into how these diverse patterns might evolve. We present a simple optimal life history model and consider circumstances in which fertility might rise or fall with age. In our model, without assuming that costs per birth rise with age, that foraging efficiency declines, or that net intergenerational transfers increase, we find that optimal fertility would tend to rise rather than decline. This happens because less energy would be allocated to survival at older ages, leaving more to allocate to fertility. In our analysis, optimal fertility could decline at older ages when an older female makes heavy net intergenerational transfers to multiple offspring or grandoffspring, reducing resources for her own reproduction. This pattern is more likely to evolve when costs of fertility at older ages are higher, when costs of reducing juvenile mortality are low, and when the level of juvenile mortality is high. We also derive conditions for the evolution of menopause, for determinate growth, and for juvenile mortality that declines with age. The optimal life history can exhibit a variety of age patterns of fertility, rising, flat, or falling, depending on the constraints and opportunities faced.
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4
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Kreider JJ, Kramer BH, Komdeur J, Pen I. The evolution of ageing in cooperative breeders. Evol Lett 2022; 6:450-459. [PMID: 36579168 PMCID: PMC9783459 DOI: 10.1002/evl3.307] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2022] [Revised: 10/24/2022] [Accepted: 11/06/2022] [Indexed: 12/03/2022] Open
Abstract
Cooperatively breeding animals live longer than their solitary counterparts. This has been suggested for birds, mole rats, and social insects. A common explanation for these long lifespans is that cooperative breeding evolves more readily in long-lived species because lower mortality reduces the rate of territory turnover and thus leads to a limitation of breeding territories. Here, we reverse this argument and show that-rather than being a cause for its evolution-long lifespans are an evolutionary consequence of cooperative breeding. In evolutionary individual-based simulations, we show that natural selection favors a delayed onset of senescence in cooperative breeders, relative to solitary breeders, because cooperative breeders have a delayed age of first reproduction as helpers wait in a reproductive queue to obtain breeder status. Especially long lifespans evolve in cooperative breeders in which queue positions depend on the helpers' age rank among the helpers within the breeding territory. Furthermore, we show that lower genetic relatedness among group members leads to the evolution of longer lifespans. This is because selection against higher mortality is weaker when mortality reduces competition for breeding between relatives. Our results link the evolutionary theory of ageing with kin selection theory, demonstrating that the evolution of ageing in cooperative breeders is driven by the timing of reproduction and kin structure within breeding territories.
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Affiliation(s)
- Jan J. Kreider
- Theoretical Research in Evolutionary Life Sciences, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands,Behavioural and Physiological Ecology, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands
| | - Boris H. Kramer
- Theoretical Research in Evolutionary Life Sciences, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands
| | - Jan Komdeur
- Behavioural and Physiological Ecology, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands
| | - Ido Pen
- Theoretical Research in Evolutionary Life Sciences, Groningen Institute for Evolutionary Life SciencesUniversity of GroningenGroningen9747 AGThe Netherlands
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5
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Davison R, Gurven M. The importance of elders: Extending Hamilton's force of selection to include intergenerational transfers. Proc Natl Acad Sci U S A 2022; 119:e2200073119. [PMID: 35867741 PMCID: PMC9282300 DOI: 10.1073/pnas.2200073119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2022] [Accepted: 04/27/2022] [Indexed: 11/18/2022] Open
Abstract
In classical evolutionary models, the force of natural selection diminishes with age toward zero by last reproduction. However, intergenerational resource transfers and other late-life contributions in social species may select for postreproductive longevity. We present a formal framework for estimating indirect fitness contributions via production transfers in a skills-intensive foraging niche, reflecting kinship and cooperation among group members. Among contemporary human hunter-gatherers and horticulturalists, indirect fitness contributions from transfers exceed direct reproductive contributions from before menopause until ages when surpluses end, around the modal age of adult death (∼70 y). Under reasonable assumptions, these benefits are the equivalent to having up to several more offspring after age 50. Despite early independence, minimal production surplus, and a shorter lifespan, chimpanzees could theoretically make indirect contributions if they adopted reliable food-sharing practices. Our results for chimpanzees hypothetically adopting hunter-gatherer subsistence suggest that a skills-intensive foraging ecology with late independence and late peak production could select for human-like life histories via positive feedback between longevity and late-life transfers. In contrast, life history changes preceding subsistence shifts would not favor further life extension or subsistence shifts. Our results formalize the theory that longevity can be favored under socioecological conditions characterized by parental and alloparental care funded through transfers of mid- to late-life production surpluses. We also extend our analysis beyond food transfers to illustrate the potential for indirect fitness contributions from pedagogy, or information transfers. While we focus mostly on humans, our approach is adaptable to any context or species where transfers can affect fitness.
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Affiliation(s)
- Raziel Davison
- Department of Anthropology, University of California, Santa Barbara, CA 93106
- Broom Center for Demography, University of California, Santa Barbara, CA 93106
| | - Michael Gurven
- Department of Anthropology, University of California, Santa Barbara, CA 93106
- Broom Center for Demography, University of California, Santa Barbara, CA 93106
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A Conceptual Framework for Food Sharing as Collaborative Consumption. Foods 2022; 11:foods11101422. [PMID: 35626993 PMCID: PMC9141114 DOI: 10.3390/foods11101422] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2022] [Revised: 05/10/2022] [Accepted: 05/11/2022] [Indexed: 11/30/2022] Open
Abstract
Food waste has increased significantly and become a global issue amidst a growing concern regarding famine in several countries. Food sharing constitutes the solution to the problem provided an appropriate framework is developed that guides its application. The sharing economy was touted as the appropriate framework, yet it is excessively macroscopic to be able to capture the dynamics of food sharing activities. A microscopic framework is required to overcome this problem, the concept of collaborative consumption with its focus on activity level being one potential solution. However, an investigation into how food sharing activities can be viewed as collaborative consumption should be completed. This paper presents an analysis of the relationship between food sharing activities and collaborative consumption. The authors employed a systematic literature review conducted by meta-analysis and content analysis to identify the commonalities between the two and the theories underlying them. The result is a conceptual framework of food sharing activities as a collaborative consumption practice. The framework highlights eight propositions that can explain the intention, performance, and continuity of food sharing activities. At the end of the paper, the authors outline the theoretical and managerial contributions and recommend future research activities.
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7
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Le A, Hawkes K, Kim PS. Male mating choices: The drive behind menopause? Theor Popul Biol 2022; 145:126-135. [PMID: 35525440 DOI: 10.1016/j.tpb.2022.04.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2021] [Revised: 01/29/2022] [Accepted: 04/24/2022] [Indexed: 11/28/2022]
Abstract
When we examine the life history of humans against our closest primate relatives, the other great apes, there is notably a greater longevity in humans which includes a distinctive postmenopausal life stage, leading to the question, "How did human females evolve to have old-age infertility?" In their paper "Mate choice and the origin of menopause" (Morton et al., 2013), Morton et al. developed an agent-based model (ABM) to investigate the novel hypothesis that ancestral male mating choices, particularly forgoing mating with older females, was the driving force behind the evolution of menopause. From their model, they concluded that indeed male preference for young female mates could have driven females to lose fertility at older ages through deleterious mutations, leading to menopause. In this work, we revisit their male-mate-choice hypothesis by formulating an analogous mathematical model using a system of ordinary differential equations (ODEs). We first show that our ODE model recreates the qualitative behaviour and hence conclusions of key scenarios in Morton et al. (2013). However, since our ODE system is less computationally demanding than their ABM, we also conduct a broader sensitivity analysis over a range of parameters and differing initial conditions to analyse the dependence on their conclusions to underlying assumptions. Our results challenge those of Morton et al. as we find that even the slightest deviation from an exclusive mating preference for younger females would counteract the evolution of menopause. Consequently, we propose that their male-mate-choice hypothesis is incomplete and needs further explanation of how a male strategy to exclusively mate with young females could have arisen in our common ancestors and remained evolutionary stable for long enough to drive the evolution of old-age female infertility.
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Affiliation(s)
- Anthia Le
- School of Mathematics and Physics, The University of Queensland, Brisbane, Australia.
| | - Kristen Hawkes
- Department of Anthropology, University of Utah, Salt Lake City, USA
| | - Peter S Kim
- School of Mathematics and Statistics, The University of Sydney, Sydney, Australia
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8
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Cubaynes S, Aars J, Yoccoz NG, Pradel R, Wiig Ø, Ims RA, Gimenez O. Modeling the demography of species providing extended parental care: A capture-recapture multievent model with a case study on polar bears ( Ursus maritimus). Ecol Evol 2021; 11:3380-3392. [PMID: 33841791 PMCID: PMC8019049 DOI: 10.1002/ece3.7296] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2020] [Revised: 01/07/2021] [Accepted: 01/25/2021] [Indexed: 12/26/2022] Open
Abstract
In species providing extended parental care, one or both parents care for altricial young over a period including more than one breeding season. We expect large parental investment and long-term dependency within family units to cause high variability in life trajectories among individuals with complex consequences at the population level. So far, models for estimating demographic parameters in free-ranging animal populations mostly ignore extended parental care, thereby limiting our understanding of its consequences on parents and offspring life histories.We designed a capture-recapture multievent model for studying the demography of species providing extended parental care. It handles statistical multiple-year dependency among individual demographic parameters grouped within family units, variable litter size, and uncertainty on the timing at offspring independence. It allows for the evaluation of trade-offs among demographic parameters, the influence of past reproductive history on the caring parent's survival status, breeding probability, and litter size probability, while accounting for imperfect detection of family units. We assess the model performance using simulated data and illustrate its use with a long-term dataset collected on the Svalbard polar bears (Ursus maritimus).Our model performed well in terms of bias and mean square error and in estimating demographic parameters in all simulated scenarios, both when offspring departure probability from the family unit occurred at a constant rate or varied during the field season depending on the date of capture. For the polar bear case study, we provide estimates of adult and dependent offspring survival rates, breeding probability, and litter size probability. Results showed that the outcome of the previous reproduction influenced breeding probability.Overall, our results show the importance of accounting for i) the multiple-year statistical dependency within family units, ii) uncertainty on the timing at offspring independence, and iii) past reproductive history of the caring parent. If ignored, estimates obtained for breeding probability, litter size, and survival can be biased. This is of interest in terms of conservation because species providing extended parental care are often long-living mammals vulnerable or threatened with extinction.
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Affiliation(s)
- Sarah Cubaynes
- CEFEUniv MontpellierCNRSEPHE‐PSL UniversityIRDUniv Paul Valéry Montpellier 3MontpellierFrance
| | - Jon Aars
- Norwegian Polar InstituteFRAM CentreTromsøNorway
| | - Nigel G. Yoccoz
- Department of Arctic and Marine BiologyUiT The Arctic University of NorwayTromsøNorway
| | - Roger Pradel
- CEFEUniv MontpellierCNRSEPHE‐PSL UniversityIRDUniv Paul Valéry Montpellier 3MontpellierFrance
| | - Øystein Wiig
- Natural History MuseumUniversity of OsloOsloNorway
| | - Rolf A. Ims
- Department of Arctic and Marine BiologyUiT The Arctic University of NorwayTromsøNorway
| | - Olivier Gimenez
- CEFEUniv MontpellierCNRSEPHE‐PSL UniversityIRDUniv Paul Valéry Montpellier 3MontpellierFrance
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9
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Abstract
Resource sharing has always been a central component of human sociality. Children require heavy investments in human capital; during working years, help is needed due to illness, disability, or bad luck. While hunter-gatherer elders assisted their descendants, more recently, elderly withdraw from work and require assistance as well. Willingness to share has been critically important for our past evolutionary success and our present daily lives. Here, we document a strong linear relationship between the public and private sharing generosity of a society and the average length of life of its members. Our findings from 34 countries on six continents suggest that survival is higher in societies that provide more support and care for one another. We suggest that this support reduces mortality by meeting urgent material needs, but also that sharing generosity may reflect the strength of social connectedness, which itself benefits human health and wellbeing and indirectly raises survival.
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10
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Lieshout SHJ, Bretman A, Newman C, Buesching CD, Macdonald DW, Dugdale HL. Individual variation in early‐life telomere length and survival in a wild mammal. Mol Ecol 2019; 28:4152-4165. [DOI: 10.1111/mec.15212] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 07/12/2019] [Accepted: 07/23/2019] [Indexed: 12/18/2022]
Affiliation(s)
- Sil H. J. Lieshout
- School of Biology Faculty of Biological Sciences University of Leeds Leeds UK
- NERC Biomolecular Analysis Facility Department of Animal and Plant Sciences University of Sheffield Sheffield UK
| | - Amanda Bretman
- School of Biology Faculty of Biological Sciences University of Leeds Leeds UK
| | - Chris Newman
- Wildlife Conservation Research Unit Department of Zoology University of Oxford Abingdon UK
| | - Christina D. Buesching
- Wildlife Conservation Research Unit Department of Zoology University of Oxford Abingdon UK
| | - David W. Macdonald
- Wildlife Conservation Research Unit Department of Zoology University of Oxford Abingdon UK
| | - Hannah L. Dugdale
- School of Biology Faculty of Biological Sciences University of Leeds Leeds UK
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11
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Vedder O, Zhang H, Dänhardt A, Bouwhuis S. Age-Specific Offspring Mortality Economically Tracks Food Abundance in a Piscivorous Seabird. Am Nat 2019; 193:588-597. [DOI: 10.1086/702304] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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12
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Berger V, Lemaître JF, Allainé D, Gaillard JM, Cohas A. Early and Adult Social Environments Shape Sex-Specific Actuarial Senescence Patterns in a Cooperative Breeder. Am Nat 2018; 192:525-536. [PMID: 30205028 DOI: 10.1086/699513] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Sociality modulates life-history traits through changes in resource allocation to fitness-related traits. However, how social factors at different stages of the life cycle modulate senescence remains poorly understood. To address this question, we assessed the influence of social environment in both early life and adulthood on actuarial senescence in the Alpine marmot, a cooperative breeder. The influence of helpers on actuarial senescence strongly differed depending on when help was provided and on the sex of the dominant. Being helped when adult slowed down senescence in both sexes. However, the effect of the presence of helpers during the year of birth of a dominant was sex specific. Among dominants helped during adulthood, females born in the presence of helpers senesced slower, whereas males senesced faster. Among dominants without helpers during adulthood, females with helpers at birth senesced faster. Social environment modulates senescence but acts differently between sexes and life stages.
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13
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Barthold Jones JA, Lenart A, Baudisch A. Complexity of the relationship between life expectancy and overlap of lifespans. PLoS One 2018; 13:e0197985. [PMID: 30001385 PMCID: PMC6042694 DOI: 10.1371/journal.pone.0197985] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2016] [Accepted: 02/22/2018] [Indexed: 01/01/2023] Open
Abstract
Longevity has long been recognised as a key facilitator of reciprocal altruism because repeated cooperation of partners hinges on mutual survival. Although demographic tools can be used to quantify mutual survival and expected overlapping lifespans, studies on the evolutionary theory of cooperation take only limited advantage of demography. Overlap of lifespans depends on variation in survival across ages and can be high or low independently of high or low life expectancies. Here we develop formal demographic measures to study the complex relationships between shared life expectancy of two birth cohort peers, the proportion of their lives that they can expect to overlap, and longevity. We simulate age-specific mortality schedules using a Siler model to reveal how infant and senescent mortality, along with age-independent mortality, affect the relationship between the proportion of life shared and life expectancy. We find that while the proportion of life shared can vary vastly for similar life expectancies, almost all changes to mortality schedules that result in higher life expectancies also result in higher proportions of life shared. A distinct exception occurs if life expectancy increases due to lowering the rate of senescence. In this case the proportion of life shared decreases. Our work shows that almost all selective pressures that result in higher life expectancies also result in a larger proportion of life shared. Therefore, selective forces that extend life also improve the chances that a cooperative system would be stable in terms of reciprocal interactions. Since reciprocal interactions may also reduce mortality and result in a feedback loop with the evolution of longevity, our measures and findings can be used for future cross-species comparisons that aim to disentangle predecessor and successor in the evolution of longevity and cooperation.
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Affiliation(s)
- Julia A. Barthold Jones
- Max-Planck Odense Center on the Biodemography of Aging, University of Southern Denmark, Odense, Denmark
- Department of Public Health, University of Southern Denmark, Odense, Denmark
- * E-mail:
| | - Adam Lenart
- Max-Planck Odense Center on the Biodemography of Aging, University of Southern Denmark, Odense, Denmark
- Department of Public Health, University of Southern Denmark, Odense, Denmark
| | - Annette Baudisch
- Max-Planck Odense Center on the Biodemography of Aging, University of Southern Denmark, Odense, Denmark
- Department of Public Health, University of Southern Denmark, Odense, Denmark
- Department of Biology, University of Southern Denmark, Odense, Denmark
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Gurven M, Stieglitz J, Trumble B, Blackwell AD, Beheim B, Davis H, Hooper P, Kaplan H. The Tsimane Health and Life History Project: Integrating anthropology and biomedicine. Evol Anthropol 2017; 26:54-73. [PMID: 28429567 PMCID: PMC5421261 DOI: 10.1002/evan.21515] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Indexed: 12/21/2022]
Abstract
The Tsimane Health and Life History Project, an integrated bio-behavioral study of the human life course, is designed to test competing hypotheses of human life-history evolution. One aim is to understand the bidirectional connections between life history and social behavior in a high-fertility, kin-based context lacking amenities of modern urban life (e.g. sanitation, banks, electricity). Another aim is to understand how a high pathogen burden influences health and well-being during development and adulthood. A third aim addresses how modernization shapes human life histories and sociality. Here we outline the project's goals, history, and main findings since its inception in 2002. We reflect on the implications of current findings and highlight the need for more coordinated ethnographic and biomedical study of contemporary nonindustrial populations to address broad questions that can situate evolutionary anthropology in a key position within the social and life sciences.
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Affiliation(s)
- Michael Gurven
- Department of AnthropologyUniversity of California‐Santa BarbaraSanta Barbara CA
| | | | - Benjamin Trumble
- Center for Evolution and Medicine; School of Human Evolution and Social ChangeArizona State UniversityTempeAZ
| | - Aaron D. Blackwell
- Department of AnthropologyUniversity of California‐Santa BarbaraSanta Barbara CA
| | - Bret Beheim
- Department of Human Behavior, Ecology and CultureMax Planck Institute for Evolutionary AnthropologyLeipzigGermany
| | - Helen Davis
- Department of AnthropologyUniversity of UtahSalt Lake CityUT
| | | | - Hillard Kaplan
- Department of AnthropologyUniversity of New MexicoAlbuquerqueNM
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15
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Brown JS, Aktipis CA. Inclusive fitness effects can select for cancer suppression into old age. Philos Trans R Soc Lond B Biol Sci 2016; 370:rstb.2015.0160. [PMID: 26056358 PMCID: PMC4581037 DOI: 10.1098/rstb.2015.0160] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Natural selection can favour health at youth or middle age (high reproductive value) over health at old age (low reproductive value). This means, all else being equal, selection for cancer suppression should dramatically drop after reproductive age. However, in species with significant parental investment, the capacity to enhance inclusive fitness may increase the reproductive value of older individuals or even those past reproductive age. Variation in parental investment levels could therefore contribute to variation in cancer susceptibility across species. In this article, we describe a simple model and framework for the evolution of cancer suppression with varying levels of parental investment and use this model to make testable predictions about variation in cancer suppression across species. This model can be extended to show that selection for cancer suppression is stronger in species with cooperative breeding systems and intergenerational transfers. We consider three cases that can select for cancer suppression into old age: (i) extended parental care that increases the survivorship of their offspring, (ii) grandparents contributing to higher fecundity of their children and (iii) cooperative breeding where helpers forgo reproduction or even survivorship to assist parents in having higher fecundity.
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Affiliation(s)
- Joel S Brown
- Department of Biological Sciences, Cancer Center, University of Illinois at Chicago, Chicago, IL 60612, USA Cancer Biology and Evolution Program, Moffitt Cancer Center, Tampa, FL 33612, USA
| | - C Athena Aktipis
- Department of Psychology, Center for Social Dynamics and Complexity, Center for Evolution and Medicine, Arizona State University, Tempe, AZ 85287-4501, USA Center for Evolution and Cancer, University of California San Francisco, San Francisco, CA 94143, USA
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16
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Evolution of longevity, age at last birth and sexual conflict with grandmothering. J Theor Biol 2016; 393:145-57. [PMID: 26796225 DOI: 10.1016/j.jtbi.2015.12.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2015] [Revised: 11/27/2015] [Accepted: 12/16/2015] [Indexed: 11/21/2022]
Abstract
We use a two-sex partial differential equation (PDE) model based on the Grandmother hypothesis. We build on an earlier model by Kim et al. (2014) by allowing for evolution in both longevity and age at last birth, and also assuming that post-fertile females support only their daughters' fertility. Similarly to Kim et al. (2014), we find that only two locally stable equilibria exist: one corresponding to great ape-like longevities and the other corresponding to hunter-gatherer longevities. Our results show that grandmothering enables the transition between these two equilibria, without extending the end of fertility. Moreover, sensitivity analyses of the model show that male competition, arising from a skew in the mating sex ratio towards males, plays a significant role in determining whether the transition from great ape-like longevities to higher longevities is possible and the equilibrium value of the average adult lifespan. Whereas grandmothering effects have a significant impact on the equilibrium value of the average age at last birth and enable the transition to higher longevities, they have an insignificant impact on the equilibrium value of the average adult lifespan.
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17
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Libertini G. Phylogeny of aging and related phenoptotic phenomena. BIOCHEMISTRY (MOSCOW) 2015; 80:1529-46. [DOI: 10.1134/s0006297915120019] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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18
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Human-specific derived alleles of CD33 and other genes protect against postreproductive cognitive decline. Proc Natl Acad Sci U S A 2015; 113:74-9. [PMID: 26621708 DOI: 10.1073/pnas.1517951112] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The individuals of most vertebrate species die when they can no longer reproduce. Humans are a rare exception, having evolved a prolonged postreproductive lifespan. Elders contribute to cooperative offspring care, assist in foraging, and communicate important ecological and cultural knowledge, increasing the survival of younger individuals. Age-related deterioration of cognitive capacity in humans compromises these benefits and also burdens the group with socially costly members. We investigated the contribution of the immunoregulatory receptor CD33 to a uniquely human postreproductive disease, Alzheimer's dementia. Surprisingly, even though selection at advanced age is expected to be weak, a CD33 allele protective against Alzheimer's disease is derived and unique to humans and favors a functional molecular state of CD33 resembling that of the chimpanzee. Thus, derived alleles may be compensatory and restore interactions altered as a consequence of human-specific brain evolution. We found several other examples of derived alleles at other human loci that protect against age-related cognitive deterioration arising from neurodegenerative disease or cerebrovascular insufficiency. Selection by inclusive fitness may be strong enough to favor alleles protecting specifically against cognitive decline in postreproductive humans. Such selection would operate by maximizing the contributions of postreproductive individuals to the fitness of younger kin.
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Primate sociality to human cooperation. Why us and not them? HUMAN NATURE-AN INTERDISCIPLINARY BIOSOCIAL PERSPECTIVE 2015; 25:28-48. [PMID: 24307447 DOI: 10.1007/s12110-013-9184-x] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Developmental psychologists identify propensities for social engagement in human infants that are less evident in other apes; Sarah Hrdy links these social propensities to novel features of human childrearing. Unlike other ape mothers, humans can bear a new baby before the previous child is independent because they have help. This help alters maternal trade-offs and so imposes new selection pressures on infants and young children to actively engage their caretakers' attention and commitment. Such distinctive childrearing is part of our grandmothering life history. While consequences for other cooperative activities must surely follow, the novel rearing environments set up by helpful grandmothering can explain why natural selection escalated preferences and motivations for interactivity in our lineage in the first place, and why, unlike other aspects of infant development, social sensitivities are not delayed in humans compared with genus Pan.
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Hooper PL, Gurven M, Winking J, Kaplan HS. Inclusive fitness and differential productivity across the life course determine intergenerational transfers in a small-scale human society. Proc Biol Sci 2015; 282:20142808. [PMID: 25673684 PMCID: PMC4345452 DOI: 10.1098/rspb.2014.2808] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2014] [Accepted: 01/14/2015] [Indexed: 12/23/2022] Open
Abstract
Transfers of resources between generations are an essential element in current models of human life-history evolution accounting for prolonged development, extended lifespan and menopause. Integrating these models with Hamilton's theory of inclusive fitness, we predict that the interaction of biological kinship with the age-schedule of resource production should be a key driver of intergenerational transfers. In the empirical case of Tsimane' forager-horticulturalists in Bolivian Amazonia, we provide a detailed characterization of net transfers of food according to age, sex, kinship and the net need of donors and recipients. We show that parents, grandparents and siblings provide significant net downward transfers of food across generations. We demonstrate that the extent of provisioning responds facultatively to variation in the productivity and demographic composition of families, as predicted by the theory. We hypothesize that the motivation to provide these critical transfers is a fundamental force that binds together human nuclear and extended families. The ubiquity of three-generational families in human societies may thus be a direct reflection of fundamental evolutionary constraints on an organism's life-history and social organization.
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Affiliation(s)
- Paul L Hooper
- Department of Anthropology, Emory University, 1557 Dickey Drive, Atlanta, GA 30322, USA Santa Fe Institute, 1399 Hyde Park Road, Santa Fe, NM 87501, USA
| | - Michael Gurven
- Department of Anthropology, University of California Santa Barbara, Santa Barbara, CA 93106, USA
| | - Jeffrey Winking
- Department of Anthropology, Texas A&M University, Mailstop 4352, College Station, TX 77843, USA
| | - Hillard S Kaplan
- Department of Anthropology, University of New Mexico, MSC01-1040, Albuquerque, NM 87131, USA
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Yiengprugsawan V, Banwell C, Takeda W, Dixon J, Seubsman SA, Sleigh AC. Health, happiness and eating together: what can a large Thai cohort study tell us? Glob J Health Sci 2015; 7:270-7. [PMID: 25946941 PMCID: PMC4802060 DOI: 10.5539/gjhs.v7n4p270] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 11/25/2014] [Indexed: 11/12/2022] Open
Abstract
Our research investigates the significance of frequent solo consumption of main meals and the association with a holistic wellbeing measure of happiness using data from 39820 Thai Cohort Study members who completed 8-year follow-up in 2013. This nationwide cohort has been under study since 2005 to analyse the dynamics and determinants of the health-risk transition from infectious to chronic diseases. Here we analyse data from the 2009 and 2013 follow-ups. Approximately 11% reported eating more than half of the main meals per week alone. Sociodemographic attributes associated with eating alone were being male, older age, unmarried, smaller household, lower income, and urban residence. Dissatisfaction with amount of spare time (ie 'busyness') was also linked to eating alone. In the multivariate cross-sectional model, reporting being unhappy was associated with frequent solo eating (Adjusted Odds Ratio - AOR 1.54, 95% Confidence Intervals 1.30-1.83). Stratified by age and sex groups, the effects were strongest among females (AOR 1.90 1.52-2.38). A monotonic relationship linked frequent eating alone and 4-year longitudinal unhappiness. The larger the dose of unhappiness the greater the odds of eating alone - AOR 1.29, 1.31, 1.72 after controlling for potential covariates. Having a meal is not only important for nutritional and health outcomes; it is also a vital part of daily social interaction. Our study provided empirical evidence from a non-Western setting that sharing meals could contribute to increasing happiness.
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Blaser MJ, Webb GF. Host demise as a beneficial function of indigenous microbiota in human hosts. mBio 2014; 5:e02262-14. [PMID: 25516618 PMCID: PMC4271553 DOI: 10.1128/mbio.02262-14] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2014] [Accepted: 11/14/2014] [Indexed: 01/12/2023] Open
Abstract
UNLABELLED The age structure of human populations is exceptional among animal species. Unlike with most species, human juvenility is extremely extended, and death is not coincident with the end of the reproductive period. We examine the age structure of early humans with models that reveal an extraordinary balance of human fertility and mortality. We hypothesize that the age structure of early humans was maintained by mechanisms incorporating the programmed death of senescent individuals, including by means of interactions with their indigenous microorganisms. First, before and during reproductive life, there was selection for microbes that preserve host function through regulation of energy homeostasis, promotion of fecundity, and defense against competing high-grade pathogens. Second, we hypothesize that after reproductive life, there was selection for organisms that contribute to host demise. While deleterious to the individual, the presence of such interplay may be salutary for the overall host population in terms of resource utilization, resistance to periodic diminutions in the food supply, and epidemics due to high-grade pathogens. We provide deterministic mathematical models based on age-structured populations that illustrate the dynamics of such relationships and explore the relevant parameter values within which population viability is maintained. We argue that the age structure of early humans was robust in its balance of the juvenile, reproductive-age, and senescent classes. These concepts are relevant to issues in modern human longevity, including inflammation-induced neoplasia and degenerative diseases of the elderly, which are a legacy of human evolution. IMPORTANCE The extended longevity of modern humans is a very recent societal artifact, although it is inherent in human evolution. The age structure of early humans was balanced by fertility and mortality, with an exceptionally prolonged juvenility. We examined the role of indigenous microbes in early humans as fundamental contributors to this age structure. We hypothesize that the human microbiome evolved mechanisms specific to the mortality of senescent individuals among early humans because their mortality contributed to the stability of the general population. The hypothesis that we present provides new bases for modern medical problems, such as inflammation-induced neoplasia and degenerative diseases of the elderly. We postulate that these mechanisms evolved because they contributed to the stability of early human populations, but their legacy is now a burden on human longevity in the changed modern world.
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Affiliation(s)
| | - Glenn F Webb
- Department of Mathematics, Vanderbilt University, Nashville, Tennessee, USA
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Stutz AJ. Modeling the pre-industrial roots of modern super-exponential population growth. PLoS One 2014; 9:e105291. [PMID: 25141019 PMCID: PMC4139354 DOI: 10.1371/journal.pone.0105291] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2014] [Accepted: 07/22/2014] [Indexed: 11/18/2022] Open
Abstract
To Malthus, rapid human population growth—so evident in 18th Century Europe—was obviously unsustainable. In his Essay on the Principle of Population, Malthus cogently argued that environmental and socioeconomic constraints on population rise were inevitable. Yet, he penned his essay on the eve of the global census size reaching one billion, as nearly two centuries of super-exponential increase were taking off. Introducing a novel extension of J. E. Cohen's hallmark coupled difference equation model of human population dynamics and carrying capacity, this article examines just how elastic population growth limits may be in response to demographic change. The revised model involves a simple formalization of how consumption costs influence carrying capacity elasticity over time. Recognizing that complex social resource-extraction networks support ongoing consumption-based investment in family formation and intergenerational resource transfers, it is important to consider how consumption has impacted the human environment and demography—especially as global population has become very large. Sensitivity analysis of the consumption-cost model's fit to historical population estimates, modern census data, and 21st Century demographic projections supports a critical conclusion. The recent population explosion was systemically determined by long-term, distinctly pre-industrial cultural evolution. It is suggested that modern globalizing transitions in technology, susceptibility to infectious disease, information flows and accumulation, and economic complexity were endogenous products of much earlier biocultural evolution of family formation's embeddedness in larger, hierarchically self-organizing cultural systems, which could potentially support high population elasticity of carrying capacity. Modern super-exponential population growth cannot be considered separately from long-term change in the multi-scalar political economy that connects family formation and intergenerational resource transfers to wider institutions and social networks.
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Affiliation(s)
- Aaron Jonas Stutz
- Division of History & Social Sciences, Oxford College of Emory University, Oxford, Georgia, United States of America
- Department of Anthropology, Emory University, Atlanta, Georgia, United States of America
- * E-mail:
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Tackney J, Cawthon RM, Coxworth JE, Hawkes K. Blood cell telomere lengths and shortening rates of chimpanzee and human females. Am J Hum Biol 2014; 26:452-60. [PMID: 24633909 DOI: 10.1002/ajhb.22538] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2013] [Revised: 02/07/2014] [Accepted: 02/17/2014] [Indexed: 12/31/2022] Open
Abstract
OBJECTIVES Slower rates of aging distinguish humans from our nearest living cousins. Chimpanzees rarely survive their forties while large fractions of women are postmenopausal even in high-mortality hunter-gatherer populations. Cellular and molecular mechanisms for these somatic aging differences remain to be identified, though telomeres might play a role. To find out, we compared telomere lengths across age-matched samples of female chimpanzees and women. METHODS We used a monochrome multiplex quantitative polymerase chain reaction to assay canonical telomere repeats in blood cells from captive female chimpanzees (65 individuals; age: 6.2-56.7 years) and compared them to the same measure in human females (43 individuals; age: 7.4-57.3 years). RESULTS Our samples showed little difference in attrition rates between the species (~0.022 T/S per year for chimpanzees and ~0.012 T/S per year for humans with overlapping 95% confidence intervals), but telomeres were twice as long in chimpanzees as in humans (T/S ratios = 2.70 and 1.26, respectively). CONCLUSIONS Based on the longevity differences, we initially hypothesized that telomere shortening rates would be faster in chimpanzees than in humans. Instead, it is shorter telomere length that appears to be the derived state in humans. This comparison indicates that better characterization of physiological aging in our closest living relatives will be indispensable for understanding the evolution of distinctive human longevity.
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Affiliation(s)
- Justin Tackney
- Department of Anthropology, University of Utah, Salt Lake City, Utah, 84112
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Kim PS, McQueen JS, Coxworth JE, Hawkes K. Grandmothering drives the evolution of longevity in a probabilistic model. J Theor Biol 2014; 353:84-94. [PMID: 24637003 DOI: 10.1016/j.jtbi.2014.03.011] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2013] [Revised: 03/05/2014] [Accepted: 03/06/2014] [Indexed: 11/27/2022]
Abstract
We present a mathematical model based on the Grandmother Hypothesis to simulate how human post-menopausal longevity could have evolved as ancestral grandmothers began to assist the reproductive success of younger females by provisioning grandchildren. Grandmothers׳ help would allow mothers to give birth to subsequent offspring sooner without risking the survival of existing offspring. Our model is an agent-based model (ABM), in which the population evolves according to probabilistic rules governing interactions among individuals. The model is formulated according to the Gillespie algorithm of determining the times to next events. Grandmother effects drive the population from an equilibrium representing a great-ape-like average adult lifespan in the lower twenties to a new equilibrium with a human-like average adult lifespan in the lower forties. The stochasticity of the ABM allows the possible coexistence of two locally-stable equilibria, corresponding to great-ape-like and human-like lifespans. Populations with grandmothering that escape the ancestral condition then shift to human-like lifespan, but the transition takes longer than previous models (Kim et al., 2012). Our simulations are consistent with the possibility that distinctive longevity is a feature of genus Homo that long antedated the appearance of our species.
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Affiliation(s)
- Peter S Kim
- School of Mathematics and Statistics, University of Sydney, NSW 2006, Australia.
| | - John S McQueen
- School of Mathematics and Statistics, University of Sydney, NSW 2006, Australia.
| | - James E Coxworth
- Department of Anthropology, University of Utah, Salt Lake City, UT 84112, USA; Utah Population Database, University of Utah, Salt Lake City, UT 84112, USA.
| | - Kristen Hawkes
- Department of Anthropology, University of Utah, Salt Lake City, UT 84112, USA.
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26
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Hawkes K, Coxworth JE. Grandmothers and the evolution of human longevity: A review of findings and future directions. Evol Anthropol 2013; 22:294-302. [DOI: 10.1002/evan.21382] [Citation(s) in RCA: 112] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Li N, Lee R, Gerland P. Extending the Lee-carter method to model the rotation of age patterns of mortality decline for long-term projections. Demography 2013; 50:2037-51. [PMID: 23904392 PMCID: PMC4550589 DOI: 10.1007/s13524-013-0232-2] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In developed countries, mortality decline is decelerating at younger ages and accelerating at old ages, a phenomenon we call "rotation." We expect that this rotation will also occur in developing countries as they attain high life expectancies. But the rotation is subtle and has proved difficult to handle in mortality models that include all age groups. Without taking it into account, however, long-term mortality projections will produce questionable results. We simplify the problem by focusing on the relative magnitude of death rates at two ages (0 and 15-19) while making assumptions about changes in rates of decline at other ages. We extend the Lee-Carter method to incorporate this subtle rotation in projection. We suggest that the extended Lee-Carter method could provide plausible projections of the age pattern of mortality for populations, including those that currently have very high life expectancies. Detailed examples are given using data from Japan and the United States.
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Affiliation(s)
- Nan Li
- Population Division, United Nations, 2 UN Plaza-DC2-1914, New York, NY, 10017, USA,
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28
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Cyrus CCY, Lee RD. On the evolution of intergenerational division of labor, menopause and transfers among adults and offspring. J Theor Biol 2013; 332:171-80. [PMID: 23648187 DOI: 10.1016/j.jtbi.2013.04.031] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 04/22/2013] [Accepted: 04/24/2013] [Indexed: 11/19/2022]
Abstract
We explain how upward transfers from adult children to their elderly parents might evolve as an interrelated feature of a deepening intergenerational division of labor. Humans have a particularly long period of juvenile dependence requiring both food and care time provided mainly by younger and older adults. We suggest that the division of labor evolves to exploit comparative advantage between young and old adults in fertility, childcare and foraging. Eventually the evolving division of labor reaches a limit when the grandmother's fertility reaches zero (menopause). Continuing, it may hit another limit when the grandmother's foraging time has been reduced to her subsistence needs. Further specialization can occur only with food transfers to the grandmother, enabling her to reduce her foraging time to concentrate on additional childcare. We prove that this outcome can arise only after menopause has evolved. We describe the conditions necessary for both group selection (comparative steady state reproductive fitness) and individual selection (successful invasion by a mutation), and interpret these conditions in terms of comparative advantages.
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Affiliation(s)
- Chu C Y Cyrus
- Institute of Economics, Academia Sinica, National Taiwan University, Taiwan.
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29
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Levitis DA, Burger O, Lackey LB. The human post-fertile lifespan in comparative evolutionary context. Evol Anthropol 2013; 22:66-79. [DOI: 10.1002/evan.21332] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2012] [Indexed: 12/26/2022]
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30
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Lee R. Intergenerational Transfers, the Biological Life Cycle, and Human Society. POPULATION AND DEVELOPMENT REVIEW 2013; 38:23-35. [PMID: 23667275 PMCID: PMC3647612 DOI: 10.1111/j.1728-4457.2013.00549.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
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Gurven M, Stieglitz J, Hooper PL, Gomes C, Kaplan H. From the womb to the tomb: the role of transfers in shaping the evolved human life history. Exp Gerontol 2012; 47:807-13. [PMID: 22595699 PMCID: PMC3437008 DOI: 10.1016/j.exger.2012.05.006] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2011] [Revised: 04/23/2012] [Accepted: 05/05/2012] [Indexed: 11/16/2022]
Abstract
Humans are the longest living and slowest growing of all primates. Although most primates are social, humans are highly cooperative and social in ways that likely co-evolved with the slow human life history. In this paper we highlight the role of resource transfers and non-material assistance within and across generations in shaping low human mortality rates. The use of complex cooperative strategies to minimize risk is a necessary precursor for selecting further reductions in mortality rate in late adulthood. In conjunction with changes in the age-profile of production, the impacts of resource transfers and other forms of cooperation on reducing mortality likely played an important role in selection on post-reproductive lifespan throughout human evolution. Using medical data and ethnographic interviews, we explore several types of common risks experienced by Tsimane forager-horticulturalists, and quantify the types and targets of aid. Our results illustrate the importance of transfers in several key domains and suggest that the absence of transfers would greatly increase human mortality rates throughout the life course.
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Affiliation(s)
- Michael Gurven
- Department of Anthropology, University of California-Santa Barbara, Santa Barbara, CA 93106, TELEPHONE: 805-893-2202, FAX: 805-893-8707
| | - Jonathan Stieglitz
- Department of Anthropology, University of New Mexico, Albuquerque, NM 87131
| | - Paul L. Hooper
- Department of Anthropology, University of New Mexico, Albuquerque, NM 87131
| | - Cristina Gomes
- Institute of Social, Behavioral and Economic Research, University of California, Santa Barbara, CA, 93106; Universidad Simón Bolivar, Departamento de Biología de Organismos, Caracas, Venezuela
| | - Hillard Kaplan
- Department of Anthropology, University of New Mexico, Albuquerque, NM 87131
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Abstract
The ageing of the population is an issue in wealthy countries worldwide because of increasing costs for health care and welfare. Survival curves taken from demographic life tables may help shed light on the hypotheses that humans are living longer and that human populations are growing older. We describe a methodology that enables us to obtain separate measurements of scale and shape variances in survival curves. Specifically, 'living longer' is associated with the scale variance of survival curves, whereas 'growing older' is associated with the shape variance. We show how the scale and shape of survival curves have changed over time during recent decades, based on period and cohort female life tables for selected wealthy countries. Our methodology will be useful for performing better tracking of ageing statistics and it is possible that this methodology can help identify the causes of current trends in human ageing.
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Affiliation(s)
- Byung Mook Weon
- X-ray Imaging Center, Department of Materials Science and Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang, 790-784, Korea
| | - Jung Ho Je
- X-ray Imaging Center, Department of Materials Science and Engineering, Pohang University of Science and Technology, San 31, Hyoja-dong, Pohang, 790-784, Korea
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Lee R, Chu CYC. The evolution of transfers and life histories. Exp Gerontol 2012; 47:803-6. [PMID: 22750486 DOI: 10.1016/j.exger.2012.06.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2012] [Revised: 06/06/2012] [Accepted: 06/19/2012] [Indexed: 11/16/2022]
Abstract
Much of life history theory analyzes life histories of independent, isolated individuals, who grow, forage, reproduce, and die. However, in many species social interactions such as food sharing are a key part of the life history strategy, altering the energetic budget constraint. Transfers and sharing raise reproductive success and also alter the fitness impact of other aspects of the life history. We discuss a variety of traits and behaviors for which transfers are important, synthesizing results from a number of earlier papers. Topics include the U-shaped mortality curve, post reproductive survival, causes of early life mortality decline, why intergenerational transfers evolve and co-evolve with longevity, time preference, sexual dimorphism and sexual differences in transfers, menopause, demographic advantages of social sharing, and consequences of social sharing for life history evolution.
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Affiliation(s)
- Ronald Lee
- Department of Demography, University of California, Berkeley, CA 94720, United States.
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Pavard S, Branger F. Effect of maternal and grandmaternal care on population dynamics and human life-history evolution: a matrix projection model. Theor Popul Biol 2012; 82:364-76. [PMID: 22326750 DOI: 10.1016/j.tpb.2012.01.007] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 01/23/2012] [Accepted: 01/23/2012] [Indexed: 11/29/2022]
Abstract
We present a matrix population model for a single-sex human population comprising non-orphan daughters (whose mothers are alive) and orphan daughters (whose mothers are dead). Orphans suffer higher mortality than non-orphans, which simulates the need for daughters to receive maternal care in order to survive. The way that maternal care affects population dynamics and life-history evolution is then analysed for demographic regimes that encompass large ranges of daughter survival, mother survival and fertility. We provide stable age-distributions of orphans and non-orphans for each regime and perform sensitivity analyses on daughter survival, adult survival and fertility. The results show that natural selection will favour (i) faster daughter independence from maternal care, (ii) higher adult survival at all ages, and (iii) early reproduction to the detriment of late reproduction. We then build scenarios concerning the coevolution of daughter survival and maternal care with adult survival and fertility. We also incorporate grandmaternal care into the model. We show that (i) the acute altriciality of human babies, (ii) the increased maternal care resulting from emergence of complex sociality and (iii) the role played by grandmothers in caring for granddaughters may have led to the emergence of specific human life-history traits: a short reproductive period characterised by a reproductive senescence and menopause, as well as an extended lifespan characterised by a post-reproductive life.
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Affiliation(s)
- Samuel Pavard
- UMR 7206 Eco-Anthropologie, Equipe Génétique desPopulations Humaines, Muséum National d'Histoire Naturelle, Paris, France.
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35
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Dominguez-Bello MG, Blaser MJ, Ley RE, Knight R. Development of the human gastrointestinal microbiota and insights from high-throughput sequencing. Gastroenterology 2011; 140:1713-9. [PMID: 21530737 PMCID: PMC10924805 DOI: 10.1053/j.gastro.2011.02.011] [Citation(s) in RCA: 256] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2010] [Revised: 02/04/2011] [Accepted: 02/09/2011] [Indexed: 12/02/2022]
Abstract
Little was known about the development of the gastrointestinal (GI) tract microbiota, until recently, because of difficulties in obtaining sufficient sequence information from enough people or time points. Now, with decreased costs of DNA sequencing and improved bioinformatic tools, we can compare GI tract bacterial communities among individuals, of all ages from infancy to adulthood. Some key recent findings are that the initial bacterial community, even in the GI tract, depends strongly on delivery mode; that the process of early development of the microbiota is highly unstable and idiosyncratic; that the microbiota differs considerably among children from different countries; and that older adults have substantially different GI tract communities than younger adults, indicating that the GI tract microbiota can change throughout life. We relate these observations to different models of evolution including the evolution of senescence and suggest that probiotics be selected based on patient age. Studies of the microbiota in older people might tell us which probiotics could increase longevity. Drug metabolism varies among individuals with different microbial communities, so age- and region-specific clinical trials are required to ensure safety and efficacy.
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Affiliation(s)
| | - Martin J. Blaser
- Departments of Medicine and Microbiology and University Langone Medical Center, New York, NY 10016
- Veterans Affairs Medical Center, New York University Langone Medical Center, New York, NY 10016
- Department of Biology, New York University, New York, NY 10003
| | - Ruth E. Ley
- Department of Microbiology, Cornell University, Ithaca, NY 14850
| | - Rob Knight
- Howard Hughes Medical Institute, Boulder, CO 80309
- Department of Chemistry & Biochemistry, University of Colorado at Boulder, Boulder, CO 80309
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Hawkes K, Kim PS, Kennedy B, Bohlender R, Hawks J. A reappraisal of grandmothering and natural selection. Proc Biol Sci 2011; 278:1936-8; discussion 1939-41. [PMID: 21471113 DOI: 10.1098/rspb.2010.2720] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Kristen Hawkes
- Department of Anthropology, University of Utah, 270 S 1400 E Room 102, Salt Lake City, UT 84112, USA.
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37
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Levitis DA, Lackey LB. A measure for describing and comparing post-reproductive lifespan as a population trait. Methods Ecol Evol 2011; 2:446-453. [PMID: 22081792 DOI: 10.1111/j.2041-210x.2011.00095.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
1. While-classical life-history theory does not predict post-reproductive lifespan (PRLS), it has been detected in a great number of taxa, leading to the view that it is a broadly conserved trait, and attempts to reconcile theory with these observations. We suggest an alternative: the apparently wide distribution of significant PRLS is an artifact of insufficient methods.2. PRLS is traditionally measured in units of time between each individual's last parturition and death, after excluding those individuals for whom this interval is short. A mean of this measure is then calculated as a population value. We show this traditional population measure (which we denote PrT) to be inconsistently calculated, inherently biased, strongly correlated with overall longevity, uninformative on the importance of PRLS in a population's life-history, unable to use the most-commonly available form of relevant data and without a realistic null hypothesis. Using data altered to ensure that the null hypothesis is true, we find a false positive rate of 0.47 for PrT.3. We propose an alternative population measure, using life-table methods. Post-reproductive Representation (PrR) is the proportion of adult years lived which are post-reproductive. We briefly derive PrR and discuss its properties. We employ a demographic simulation, based on the null hypothesis of simultaneous and proportional decline in survivorship and fecundity, to produce a null distribution for PrR based on the age-specific rates of a population.4. In an example analysis, using data on 84 populations of human and non-human primates, we demonstrate the ability of PrR to represent the effects of artificial protection from mortality and of humanness on PRLS. PrR is found to be higher for all human populations under a wide range of conditions than for any non-human primate in our sample. A strong effect of artificial protection is found, but humans under the most-adverse conditions still achieve PrR of >0.3.5. PrT should not be used as a population measure, and should be used as an individual measure only with great caution. The use of PrR as an intuitive, statistically valid and intercomparable population life-history measure is encouraged.
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Affiliation(s)
- Daniel A Levitis
- Max Planck Institute for Demographic Research, Laboratory of Evolutionary Biodemography, Konrad-Zuse Strasse 1, 18057 Rostock Germany
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38
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Kachel AF, Premo LS, Hublin JJ. Grandmothering and natural selection. Proc Biol Sci 2011; 278:384-91. [PMID: 20739319 PMCID: PMC3013409 DOI: 10.1098/rspb.2010.1247] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2010] [Accepted: 08/05/2010] [Indexed: 11/12/2022] Open
Abstract
Humans are unique among primates in that women regularly outlive their reproductive period by decades. The grandmother hypothesis proposes that natural selection increased the length of the human post-menopausal period-and, thus, extended longevity-as a result of the inclusive fitness benefits of grandmothering. However, it has yet to be demonstrated that the inclusive fitness benefits associated with grandmothering are large enough to warrant this explanation. Here, we show that the inclusive fitness benefits are too small to affect the evolution of longevity under a wide range of conditions in simulated populations. This is due in large part to the relatively weak selection that applies to women near or beyond the end of their reproductive period. However, we find that grandmothers can facilitate the evolution of a shorter reproductive period when their help decreases the weaning age of their matrilineal grandchildren. Because selection favours a shorter reproductive period in the presence of shorter interbirth intervals, this finding holds true for any form of allocare that helps mothers resume cycling more quickly. We conclude that while grandmothering is unlikely to explain human-like longevity, allocare could have played an important role in shaping other unique aspects of human life history, such as a later age at first birth and a shorter female reproductive period.
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Affiliation(s)
- A Friederike Kachel
- Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, Deutscher Platz 6, 04103 Leipzig, Germany.
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39
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Lee RD, Mason A. Generational Economics in a Changing World. POPULATION AND DEVELOPMENT REVIEW 2011; 37:115-142. [PMID: 21804657 PMCID: PMC3143474 DOI: 10.1111/j.1728-4457.2011.00380.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
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Abstract
The age-specific mortality curve for many species, including humans, is U-shaped: mortality declines with age in the developing cohort (ontogenescence) before increasing with age (senescence). The field of evolutionary demography has long focused on understanding the evolution of senescence while largely failing to address the evolution of ontogenescence. The current review is the first to gather the few available hypotheses addressing the evolution of ontogenescence, examine the basis and assumptions of each and ask what the phylogenetic extent of ontogenescence may be. Ontogenescence is among the most widespread of life-history traits, occurring in every population for which I have found sufficiently detailed data, in major groups throughout the eukaryotes, across many causes of death and many life-history types. Hypotheses seeking to explain ontogenescence include those based on kin selection, the acquisition of robustness, heterogeneous frailties and life-history optimization. I propose a further hypothesis, arguing that mortality drops with age because most transitions that could trigger the risks caused by genetic and developmental malfunctions are concentrated in early life. Of these hypotheses, only those that frame ontogenescence as an evolutionary by-product rather than an adaptation can explain the tremendous diversity of organisms and environments in which it occurs.
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Affiliation(s)
- Daniel A Levitis
- Laboratory of Evolutionary Biodemography, Max Planck Institute for Demographic Research, Rostock, Germany.
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41
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Chu CYC, Chien HK, Lee RD. The Evolutionary Theory of Time Preferences and Intergenerational Transfers. JOURNAL OF ECONOMIC BEHAVIOR & ORGANIZATION 2010; 76:451-464. [PMID: 21218165 PMCID: PMC3014627 DOI: 10.1016/j.jebo.2010.09.011] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
At each age an organism produces energy by foraging and allocates this energy among reproduction, survival, growth, and intergenerational transfers. We characterize the optimal set of allocation decisions that maximizes fitness. Time preference (the discount rate) is derived from the marginal rate of substitution between energy obtained at two different times or ages, holding fitness constant. Time preference varies with age in different ways depending on whether an individual is immature or mature, and during the transition between these stages. We conclude that time preference and discount rates are likely to be U-shaped across age.
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Affiliation(s)
| | - Hung-Ken Chien
- Department of Economics, University of Bonn, Bonn, Germany
| | - Ronald D. Lee
- Departments of Demography and Economics, 2232 Piedmont Ave., University of California, Berkeley, CA, 94720, USA
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42
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Le Couteur DG, Simpson SJ. Adaptive senectitude: the prolongevity effects of aging. J Gerontol A Biol Sci Med Sci 2010; 66:179-82. [PMID: 20937675 DOI: 10.1093/gerona/glq171] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
In the past, it has been assumed that all the biological and medical changes that occur in old age are deleterious. It has therefore been concluded that treatment and prevention of such changes in old age should increase healthspan and delay death. However, accruing epidemiological and clinical trial evidence in older humans suggests that this is not the case. Some studies have shown that antioxidants and hormone supplements increase mortality, whereas high blood pressure, obesity, and metabolic syndrome are often associated with improved outcomes in very elderly people. Perhaps, some of these supposedly detrimental changes accompanying old age are in fact evolutionary adaptations to prolong life after reproduction in humans. Indeed, a form of reverse antagonistic pleiotropy or adaptive senectitude might be occurring. Some common biological and medical changes in old age might actually enhance longevity and represent novel targets for improving health in older people.
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Affiliation(s)
- David G Le Couteur
- Centre for Education and Research on Ageing, Concord RG Hospital, University of Sydney, Hospital Road, Concord, NSW 2139, Australia.
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43
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Kirkwood TBL, Shanley DP. The connections between general and reproductive senescence and the evolutionary basis of menopause. Ann N Y Acad Sci 2010; 1204:21-9. [PMID: 20738272 DOI: 10.1111/j.1749-6632.2010.05520.x] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We consider the relationship between the factors responsible for the general biology of aging and those that specifically influence the aging of the reproductive system. To understand this relationship it is necessary to be clear about the evolutionary forces acting on both sets of factors. Only in this way can the correct causal connections be established. Of particular significance is the existence in some species of a distinct period of postreproductive life. This is most striking in the case of the human menopause, for which a particular combination of biological and sociobiological factors appear to be responsible.
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Affiliation(s)
- Thomas B L Kirkwood
- Institute for Ageing and Health, Newcastle University, Campus for Ageing and Vitality, Newcastle upon Tyne, UK.
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44
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Food-Sharing Networks in Lamalera, Indonesia: Reciprocity, Kinship, and Distance. HUMAN NATURE-AN INTERDISCIPLINARY BIOSOCIAL PERSPECTIVE 2010; 21:243-268. [PMID: 21218145 DOI: 10.1007/s12110-010-9091-3] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Exponential random graph modeling (ERGM) is used here to test hypotheses derived from human behavioral ecology about the adaptive nature of human food sharing. Respondents in all (n=317) households in the fishing and sea-hunting village of Lamalera, Indonesia were asked to name those households to whom they had more frequently given (and from whom they had more frequently received) food during the preceding sea-hunting season. The responses were used to construct a social network of between-household food-sharing relationships in the village. The results show that kinship, proximity, and reciprocal sharing all strongly increase the probability of giving food to a household. The effects of kinship and distance are relatively independent of each other, while reciprocity is more common among residentially and genealogically close households. The results show support for reciprocal altruism as a motivation for food sharing while kinship and distance appear to be important partner-choice criteria.
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45
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Kramer KL, Ellison PT. Pooled energy budgets: Resituating human energy -allocation trade-offs. Evol Anthropol 2010. [DOI: 10.1002/evan.20265] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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46
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Abstract
What motivates grandparents to their altruism? We review answers from evolutionary theory, sociology, and economics. Sometimes in direct conflict with each other, these accounts of grandparental investment exist side-by-side, with little or no theoretical integration. They all account for some of the data, and none account for all of it. We call for a more comprehensive theoretical framework of grandparental investment that addresses its proximate and ultimate causes, and its variability due to lineage, values, norms, institutions (e.g., inheritance laws), and social welfare regimes. This framework needs to take into account that the demographic shift to low fecundity and mortality in economically developed countries has profoundly altered basic parameters of grandparental investment. We then turn to the possible impact of grandparental acts of altruism, and examine whether benefits of grandparental care in industrialized societies may manifest in terms of less tangible dimensions, such as the grandchildren's cognitive and verbal ability, mental health, and well-being. Although grandparents in industrialized societies continue to invest substantial amounts of time and money in their grandchildren, we find a paucity of studies investigating the influence that this investment has on grandchildren in low-risk family contexts. Under circumstances of duress - for example, teenage pregnancy or maternal depression - there is converging evidence that grandparents can provide support that helps to safeguard their children and grandchildren against adverse risks. We conclude by discussing the role that grandparents could play in what has been referred to as Europe's demographic suicide.
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Hawkes K. Colloquium paper: how grandmother effects plus individual variation in frailty shape fertility and mortality: guidance from human-chimpanzee comparisons. Proc Natl Acad Sci U S A 2010; 107 Suppl 2:8977-84. [PMID: 20445089 PMCID: PMC3024018 DOI: 10.1073/pnas.0914627107] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In the first paper to present formal theory explaining that senescence is a consequence of natural selection, W. D. Hamilton concluded that human postmenopausal longevity results from the contributions of ancestral grandmothers to the reproduction of their relatives. A grandmother hypothesis, subsequently elaborated with additional lines of evidence, helps explain both exceptional longevity and additional features of life history that distinguish humans from the other great apes. However, some of the variation observed in aging rates seems inconsistent with the tradeoffs between current and future reproduction identified by theory. In humans and chimpanzees, our nearest living relatives, individuals who bear offspring at faster rates do not cease bearing sooner. They continue to be fertile longer instead. Furthermore, within both species, groups with lower overall mortality rates have faster rates of increase in death risk with advancing age. These apparent contradictions to the expected life history tradeoffs likely result from heterogeneity in frailty among individuals. Whereas robust and frail alike must allocate investments between current and future reproduction, the more robust can afford more of both. This heterogeneity, combined with evolutionary tradeoffs and the key role of ancestral grandmothers they identify, helps explain aspects of human aging that increasingly concern us all.
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Affiliation(s)
- Kristen Hawkes
- Department of Anthropology, University of Utah, Salt Lake City, UT 84112
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48
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Hill K, Hurtado AM. Cooperative breeding in South American hunter-gatherers. Proc Biol Sci 2009; 276:3863-70. [PMID: 19692401 PMCID: PMC2817285 DOI: 10.1098/rspb.2009.1061] [Citation(s) in RCA: 185] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2009] [Accepted: 07/17/2009] [Indexed: 11/12/2022] Open
Abstract
Evolutionary researchers have recently suggested that pre-modern human societies habitually practised cooperative breeding and that this feature helps explain human prosocial tendencies. Despite circumstantial evidence that post-reproductive females and extra-pair males both provide resources required for successful reproduction by mated pairs, no study has yet provided details about the flow of food resources by different age and sex categories to breeders and offspring, nor documented the ratio of helpers to breeders. Here, we show in two hunter-gatherer societies of South America that each breeding pair with dependent offspring on average obtained help from approximately 1.3 non-reproductive adults. Young married males and unmarried males of all ages were the main food providers, accounting for 93-100% of all excess food production available to breeding pairs and their offspring. Thus, each breeding pair with dependants was provisioned on average by 0.8 adult male helpers. The data provide no support for the hypothesis that post-reproductive females are the main provisioners of younger reproductive-aged kin in hunter-gatherer societies. Demographic and food acquisition data show that most breeding pairs can expect food deficits owing to foraging luck, health disabilities and accumulating dependency ratio of offspring in middle age, and that extra-pair provisioning may be essential to the evolved human life history.
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Affiliation(s)
- Kim Hill
- School of Human Evolution and Social Change, Arizona State University, Tempe, AZ, USA.
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49
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Colloquium papers: Transfers and transitions: parent-offspring conflict, genomic imprinting, and the evolution of human life history. Proc Natl Acad Sci U S A 2009; 107 Suppl 1:1731-5. [PMID: 19666529 DOI: 10.1073/pnas.0904111106] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Human offspring are weaned earlier than the offspring of other great apes but take longer to reach nutritional independence. An analysis of human disorders of imprinted genes suggests genes of paternal origin, expressed in infants, have been selected to favor more intense suckling than genes of maternal origin. The same analysis suggests that genes of maternal origin may favor slower childhood growth but earlier sexual maturation. These observations are consistent with a hypothesis in which slow maturation was an adaptation of offspring that reduced maternal fitness, whereas early weaning was an adaptation of mothers that reduced the fitness of individual offspring.
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50
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Hawkes K, Smith KR, Robson SL. Mortality and fertility rates in humans and chimpanzees: How within-species variation complicates cross-species comparisons. Am J Hum Biol 2009; 21:578-86. [PMID: 19213006 PMCID: PMC6121812 DOI: 10.1002/ajhb.20890] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
A grandmother hypothesis may explain why humans evolved greater longevity while continuing to end female fertility at about the same age as do the other great apes. With that grandmother hypothesis in mind, we sought to compare age-specific mortality and fertility rates between humans and chimpanzees, our closest living relatives, and found two puzzles. First, we expected that lower adult mortality in humans would be associated with slower senescence, but the rate of chimpanzee demographic aging falls within the human range. Second, we expected declines in age-specific fertility to be similar in the two species but instead of falling in the thirties as it does in women, fertility remains high into the forties in some chimpanzee populations. We report these puzzles using data from nine human populations and both wild and captive chimpanzees, and suggest that systematic differences in the heterogeneity of surviving adults may explain them.
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Affiliation(s)
- Kristen Hawkes
- Department of Anthropology, University of Utah, Salt Lake City, 84112-0600, USA.
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