1
|
Hackman JV, Campbell BC, Hewlett B, Page AE, Kramer KL. Adipose development is consistent across hunter-gatherers and diverges from western references. Proc Biol Sci 2024; 291:20240110. [PMID: 39191279 DOI: 10.1098/rspb.2024.0110] [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] [Received: 02/15/2024] [Revised: 04/23/2024] [Accepted: 07/12/2024] [Indexed: 08/29/2024] Open
Abstract
Despite agreement that humans have evolved to be unusually fat primates, adipose patterning among hunter-gatherers has received little empirical consideration. Here we consider the development of adiposity among four contemporary groups of hunter-gatherers, the Aka, Savanna Pumé, Ju'/Hoansi and Agta using multi-level generalized additive mixed modelling to characterize the growth of tricep skinfolds from early childhood through adolescence. In contrast to references, hunter-gatherers show several consistent patterns: (i) children are lean with little fat accumulation; (ii) no adiposity rebound at 5 years is evident; (iii) girls on average have built 90% of their body size, and reach menarche when adiposity is at its maximum velocity; and (iv) a metabolic trade-off is evident in young, but not older children, such that both boys and girls prioritize skeletal growth during middle childhood, a trade-off that diminishes during adolescence when height velocity increases in pace with fat accumulation. Consistent results across hunter-gatherers living in diverse environments suggest that these patterns reflect a general forager pattern of development. The findings provide a valuable baseline for adipose development not apparent from reference populations. We emphasize both generalized trends among hunter-gatherers, and that inter-populational differences point to the plasticity with which humans organize growth and development.
Collapse
Affiliation(s)
- Joseph V Hackman
- Department of Anthropology, University of Utah , Salt Lake City, UT, USA
| | | | - Barry Hewlett
- Department of Anthropology, Washington State University , Pullman, WA, USA
| | - Abigail E Page
- Divsion of Psychology, Brunel University London , London, UK
| | - Karen L Kramer
- Department of Anthropology, University of Utah , Salt Lake City, UT, USA
| |
Collapse
|
2
|
Hackman J, Kramer KL. Kin networks and opportunities for reproductive cooperation and conflict among hunter-gatherers. Philos Trans R Soc Lond B Biol Sci 2023; 378:20210434. [PMID: 36440562 PMCID: PMC9703223 DOI: 10.1098/rstb.2021.0434] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Accepted: 10/03/2022] [Indexed: 11/29/2022] Open
Abstract
Little is known about the potential for reproductive conflict among hunter-gatherer populations, who are characterized by bilateral kinship ties, flexible residential mobility, and high offspring mortality. To assess the potential for reproductive conflict, we use longitudinal residence and reproductive history data for two bands of South American foragers. Using multilevel logistic regressions (N = 44 women, N = 712 person years), we examine how yearly measures of (i) camp composition, (ii) distribution of female kin and (iii) a woman's position in a female kinship network impact the likelihood of giving birth or experiencing a child's death. We compare conflict models to a demographic model that accounts for the proportion of women giving birth in a given year. Contrary to conflict models, results show that the odds of giving birth increase with the presence of highly related women. However, the odds of experiencing an offspring death are insensitive to the presence of coresident women. Network measures of closeness and centrality in the female kin network also show no significant effect on reproductive outcomes. Furthermore, chances of both births and deaths increase in years when proportionally more women are giving birth. We argue that demographic stochasticity relating to ecological conditions best predicts reproductive outcomes for women. This article is part of the theme issue 'Cooperation among women: evolutionary and cross-cultural perspectives'.
Collapse
Affiliation(s)
- Joseph Hackman
- Department of Anthropology, University of Utah, Salt Lake City, UT 84112, USA
| | - Karen L. Kramer
- Department of Anthropology, University of Utah, Salt Lake City, UT 84112, USA
| |
Collapse
|
3
|
Pretelli I, Ringen E, Lew-Levy S. Foraging complexity and the evolution of childhood. SCIENCE ADVANCES 2022; 8:eabn9889. [PMID: 36223468 PMCID: PMC9555775 DOI: 10.1126/sciadv.abn9889] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2022] [Accepted: 08/25/2022] [Indexed: 05/22/2023]
Abstract
Our species' long childhood is hypothesized to have evolved as a period for learning complex foraging skills. Researchers studying the development of foraging proficiency have focused on assessing this hypothesis, yet studies present inconsistent conclusions regarding the connection between foraging skill development and niche complexity. Here, we leverage published records of child and adolescent foragers from 28 societies to (i) quantify how skill-intensive different resources are and (ii) assess whether children's proficiency increases more slowly for more skill-intensive resources. We find that foraging returns increase slowly for more skill-intensive, difficult-to-extract resources (tubers and game), consistent with peak productivity attained in adulthood. Foraging returns for easier-to-extract resources (fruit and fish/shellfish) increase rapidly during childhood, with adult levels of productivity reached by adolescence. Our findings support the view that long childhoods evolved as an extended period for learning to extract complex resources characteristic of the human foraging niche.
Collapse
Affiliation(s)
- Ilaria Pretelli
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Corresponding author.
| | - Erik Ringen
- Department of Anthropology, Emory University, Atlanta, GA, USA
| | - Sheina Lew-Levy
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
- Department of Comparative Cultural Psychology, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| |
Collapse
|
4
|
Kramer KL, Campbell BC, Achenbach A, Hackman JV. Sex differences in adipose development in a hunter-gatherer population. Am J Hum Biol 2021; 34:e23688. [PMID: 34655448 DOI: 10.1002/ajhb.23688] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2021] [Revised: 09/09/2021] [Accepted: 09/28/2021] [Indexed: 12/15/2022] Open
Abstract
OBJECTIVE Humans are unusually sexually dimorphic in body composition, with adult females having on average nearly twice the fat mass as males. The development of adipose sex differences has been well characterized for children growing up in food-abundant environments, with less known about cross-cultural variation, particularly in populations without exposure to market foods, mechanized technologies, schooling, vaccination, or other medical interventions. METHODS To add to the existing cross-cultural data, we fit multiple growth curves to body composition and anthropometric data to describe adipose development for the Savanna Pumé, South American hunter-gatherers. RESULTS (1) Little evidence is found for an adiposity 'rebound' at the end of early childhood among either Savanna Pumé girls or boys. (2) Rather, fat deposition fluctuates during childhood, from age ~4 to ~9 years, with no appreciable accumulation until the onset of puberty, a pattern also observed among Congo Baka hunter-gatherers. (3) Body fat fluctuations are more pronounced for girls than boys. (4) The age of peak skeletal, weight, and adipose gains are staggered to a much greater extent among the Savanna Pumé compared to the National Health and Nutrition Examination Survey (NHANES III) reference, suggesting this is an important developmental strategy in lean populations. CONCLUSION Documenting growth patterns under diverse preindustrial energetic conditions provides an important baseline for understanding sex differences in body fat emerging today under food abundance.
Collapse
Affiliation(s)
- Karen L Kramer
- Department of Anthropology, University of Utah, Salt Lake City, Utah, USA
| | - Benjamin C Campbell
- Department of Anthropology, University of Wisconsin, Milwaukee, Wisconsin, USA
| | - Alan Achenbach
- Department of Anthropology, University of Utah, Salt Lake City, Utah, USA
| | - Joseph V Hackman
- Department of Anthropology, University of Utah, Salt Lake City, Utah, USA
| |
Collapse
|
5
|
|
6
|
Affiliation(s)
- Cara Ocobock
- Department of Anthropology University Notre Dame Notre Dame IN 46556 USA
| |
Collapse
|
7
|
Wells JCK, Stock JT. Life History Transitions at the Origins of Agriculture: A Model for Understanding How Niche Construction Impacts Human Growth, Demography and Health. Front Endocrinol (Lausanne) 2020; 11:325. [PMID: 32508752 PMCID: PMC7253633 DOI: 10.3389/fendo.2020.00325] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Accepted: 04/27/2020] [Indexed: 12/18/2022] Open
Abstract
Over recent millennia, human populations have regularly reconstructed their subsistence niches, changing both how they obtain food and the conditions in which they live. For example, over the last 12,000 years the vast majority of human populations shifted from foraging to practicing different forms of agriculture. The shift to farming is widely understood to have impacted several aspects of human demography and biology, including mortality risk, population growth, adult body size, and physical markers of health. However, these trends have not been integrated within an over-arching conceptual framework, and there is poor understanding of why populations tended to increase in population size during periods when markers of health deteriorated. Here, we offer a novel conceptual approach based on evolutionary life history theory. This theory assumes that energy availability is finite and must be allocated in competition between the functions of maintenance, growth, reproduction, and defence. In any given environment, and at any given stage during the life-course, natural selection favours energy allocation strategies that maximise fitness. We argue that the origins of agriculture involved profound transformations in human life history strategies, impacting both the availability of energy and the way that it was allocated between life history functions in the body. Although overall energy supply increased, the diet composition changed, while sedentary populations were challenged by new infectious burdens. We propose that this composite new ecological niche favoured increased energy allocation to defence (immune function) and reproduction, thus reducing the allocation to growth and maintenance. We review evidence in support of this hypothesis and highlight how further work could address both heterogeneity and specific aspects of the origins of agriculture in more detail. Our approach can be applied to many other transformations of the human subsistence niche, and can shed new light on the way that health, height, life expectancy, and fertility patterns are changing in association with globalization and nutrition transition.
Collapse
Affiliation(s)
- Jonathan C. K. Wells
- Childhood Nutrition Research Centre, Population, Policy and Practice Programme, UCL Great Ormond Street Institute of Child Health, London, United Kingdom
- *Correspondence: Jonathan C. K. Wells
| | - Jay T. Stock
- Department of Anthropology, University of Western Ontario, London, ON, Canada
- Department of Archaeology, Max Planck Institute for the Science of Human History, Jena, Germany
| |
Collapse
|
8
|
Kramer KL. How There Got to Be So Many of Us: The Evolutionary Story of Population Growth and a Life History of Cooperation. JOURNAL OF ANTHROPOLOGICAL RESEARCH 2019. [DOI: 10.1086/705943] [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]
|
9
|
Abstract
While the categories of adolescence and puberty are often treated as one, the existence of two distinct terms points to different kinds of maturation in humans. Puberty refers to a period of coordinated somatic growth and reproductive maturation that shifts individuals from nonreproductive juvenility to reproductive maturity. Adolescence includes the behavioral and social assumption of adult roles. Life history theory offers powerful tools for understanding why puberty occurs later in humans than in other primates, including the benefits of delayed reproduction as part of a cooperation-intensive life history strategy. It also sheds light on the ways that pubertal timing responds to environmental variation. I review the mechanisms of maturation in humans and propose biocultural approaches to integrate life historical understandings of puberty with a broader definition of environment to encompass the concept of adolescence.
Collapse
Affiliation(s)
- Meredith W. Reiches
- Department of Anthropology, University of Massachusetts, Boston, Massachusetts 02125, USA
| |
Collapse
|
10
|
Jazwiec PA, Sloboda DM. Nutritional adversity, sex and reproduction: 30 years of DOHaD and what have we learned? J Endocrinol 2019; 242:T51-T68. [PMID: 31013473 DOI: 10.1530/joe-19-0048] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2019] [Accepted: 03/25/2019] [Indexed: 12/12/2022]
Abstract
It is well established that early life environmental signals, including nutrition, set the stage for long-term health and disease risk - effects that span multiple generations. This relationship begins early, in the periconceptional period and extends into embryonic, fetal and early infant phases of life. Now known as the Developmental Origins of Health and Disease (DOHaD), this concept describes the adaptations that a developing organism makes in response to early life cues, resulting in adjustments in homeostatic systems that may prove maladaptive in postnatal life, leading to an increased risk of chronic disease and/or the inheritance of risk factors across generations. Reproductive maturation and function is similarly influenced by early life events. This should not be surprising, since primordial germ cells are established early in life and thus vulnerable to early life adversity. A multitude of 'modifying' cues inducing developmental adaptations have been identified that result in changes in reproductive development and impairments in reproductive function. Many types of nutritional challenges including caloric restriction, macronutrient excess and micronutrient insufficiencies have been shown to induce early life adaptations that produce long-term reproductive dysfunction. Many pathways have been suggested to underpin these associations, including epigenetic reprogramming of germ cells. While the mechanisms still remain to be fully investigated, it is clear that a lifecourse approach to understanding lifetime reproductive function is necessary. Furthermore, investigations of the impacts of early life adversity must be extended to include the paternal environment, especially in epidemiological and clinical studies of offspring reproductive function.
Collapse
Affiliation(s)
- Patrycja A Jazwiec
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Canada
- The Farncombe Family Digestive Diseases Research Institute, McMaster University, Hamilton, Canada
| | - Deborah M Sloboda
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Canada
- The Farncombe Family Digestive Diseases Research Institute, McMaster University, Hamilton, Canada
- Department of Pediatrics and Obstetrics and Gynecology, McMaster University, Hamilton, Canada
| |
Collapse
|
11
|
Šaffa G, Kubicka AM, Hromada M, Kramer KL. Is the timing of menarche correlated with mortality and fertility rates? PLoS One 2019; 14:e0215462. [PMID: 30998739 PMCID: PMC6472797 DOI: 10.1371/journal.pone.0215462] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Accepted: 04/02/2019] [Indexed: 11/20/2022] Open
Abstract
Timing of menarche has largely been studied in the context of a secular trend. However, since mortality and fertility rates are fundamental demographic factors linked to a population’s developmental and reproductive characteristics, we expect that the timing of menarche, a precondition to reproduction, is also associated with these vital rates. We conduct an analysis of 89 countries and 21 demographic, socioeconomic, nutritional, and educational variables selected for their known influence on menarche. Model results predict that a country’s fertility and adult female mortality rates are significant predictors of mean age at menarche, while other covariates are not. Specifically, menarche is delayed in countries with high mortality and high fertility, which may be proxies for assessing overall environmental quality. We emphasize that, for a comprehensive understanding of the timing of menarche, it is critical to take into account both individual- and population-level influences.
Collapse
Affiliation(s)
- Gabriel Šaffa
- Laboratory and Museum of Evolutionary Ecology, Department of Ecology, Faculty of Humanities and Natural Sciences, University of Presov, Prešov, Slovakia
- Department of Zoology, Faculty of Science, University of South Bohemia, České Budějovice, Czech Republic
| | - Anna Maria Kubicka
- Department of Zoology, University of Life Sciences in Poznań, Poznań, Poland
| | - Martin Hromada
- Laboratory and Museum of Evolutionary Ecology, Department of Ecology, Faculty of Humanities and Natural Sciences, University of Presov, Prešov, Slovakia
- Faculty of Biological Sciences, University of Zielona Góra, Zielona Góra, Poland
- * E-mail:
| | - Karen Leslie Kramer
- Department of Anthropology, University of Utah, Salt Lake City, Utah, United States of America
| |
Collapse
|
12
|
Veile A, Valeggia C, Kramer KL. Cesarean birth and the growth of Yucatec Maya and Toba/Qom children. Am J Hum Biol 2019; 31:e23228. [PMID: 30815932 DOI: 10.1002/ajhb.23228] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 01/30/2019] [Accepted: 02/03/2019] [Indexed: 01/19/2023] Open
Abstract
OBJECTIVE Cesarean delivery is often epidemiologically associated with childhood obesity. However, little attention is paid to post-birth modulatory environments, and most studies are conducted in settings where obesity arises for a number of reasons in addition to birth mode. We therefore assess population differences in the relationship between birth mode and childhood growth using data from rural and peri-urban Latin American indigenous populations, and test predictions developed using life history theory. METHODS Child height and weight were measured monthly in 80 Yucatec Maya and 58 Toba/Qom children aged 1-48 months (2007-2014, 3812 observations). Random-effects linear mixed models were used to compare children's growth by population, sex, and birth mode, accounting for potential confounders. RESULTS Cesarean delivery rates were 47% (Toba/Qom) and 20% (Yucatec Maya). Childhood obesity and overweight rates were low in both populations. Cesarean-delivered children had significantly greater weight gain (but similar height grain) compared to vaginally-delivered children. By age 4, cesarean delivered Yucatec Maya girls and boys, and Toba/Qom boys (not girls), had significantly higher weight-for-age compared to vaginally-delivered children from their own sex and population. CONCLUSIONS This provides one of the first attempts to document differences in children's growth patterns according to mode of birth in modernizing indigenous populations. Cesarean delivery is associated with young children's growth patterns, even in the absence of many obesity-inducing factors. There are also population, age, and sex differences in the relationship between birth mode and childhood weight trajectories that warrant future investigation.
Collapse
Affiliation(s)
- Amanda Veile
- Department of Anthropology, Purdue University, West Lafayette, Indiana
| | - Claudia Valeggia
- Department of Anthropology, Yale University, New Haven, Connecticut
| | - Karen L Kramer
- Department of Anthropology, University of Utah, Salt Lake City, Utah
| |
Collapse
|
13
|
Lassek WD, Gaulin SJC. Do the Low WHRs and BMIs Judged Most Attractive Indicate Higher Fertility? EVOLUTIONARY PSYCHOLOGY 2018; 16:1474704918800063. [PMID: 30296846 PMCID: PMC10480809 DOI: 10.1177/1474704918800063] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2018] [Accepted: 08/20/2018] [Indexed: 12/30/2022] Open
Abstract
We examine the widely accepted view that very low waist-hip ratios and low body mass indices (BMIs) in women in well-nourished populations are judged attractive by men because these features reliably indicate superior fertility. In both subsistence and well-nourished populations, relevant studies of fertility do not support this view. Rather studies indicate lower fertility in women with anthropometric values associated with high attractiveness. Moreover, low maternal BMI predisposes to conditions that compromise infant survival. Consistent with these findings from the literature, new data from a large U.S. sample of women past reproductive age show that women with lower BMIs in the late teens had fewer live births, controlling for education, marital history, and race. They also had later menarche and earlier menopause compared with women with higher youth BMIs. In addition, data from the 2013 U.S. natality database show that mothers with lower prepregnancy BMIs have an increased risk of producing both low-birth-weight and preterm infants controlling for other relevant variables-conditions that would have adversely affected fitness over almost all of human evolution. Thus, a review of the relevant literature and three new tests fail to support the view that highly attractive women are more fertile.
Collapse
Affiliation(s)
- William D. Lassek
- Department of Anthropology, University of California at Santa Barbara, Santa Barbara, CA, USA
| | - Steven J. C. Gaulin
- Department of Anthropology, University of California at Santa Barbara, Santa Barbara, CA, USA
| |
Collapse
|
14
|
The cooperative economy of food: Implications for human life history and physiology. Physiol Behav 2018; 193:196-204. [DOI: 10.1016/j.physbeh.2018.03.029] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Revised: 03/25/2018] [Accepted: 03/26/2018] [Indexed: 02/07/2023]
|
15
|
Ramirez Rozzi FV. Reproduction in the Baka pygmies and drop in their fertility with the arrival of alcohol. Proc Natl Acad Sci U S A 2018; 115:E6126-E6134. [PMID: 29915032 PMCID: PMC6142234 DOI: 10.1073/pnas.1719637115] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
To understand the diversity of human growth and development from an evolutionary point of view, there is an urgent need to characterize the life-history variables of vanishing forager societies. The small body size of the Baka pygmies is the outcome of a low growth rate during infancy. While the ages at sexual maturity, menarche, and first delivery are similar to those in other populations, fertility aspects are unknown. In the Le Bosquet district in Cameroon, thanks to systematic birth records kept from 1980 onwards, we were able to assign ages to individuals with certainty. This study, based on chronological records and on data collected from 2007 to 2017, presents life-history variables related to fertility and mortality among the Baka pygmies: total fertility rate, age-specific fertility rate, completed family size, reproductive span, age at menopause, and infant and juvenile mortality. The Baka present low infant and juvenile mortality, and their fertility pattern differs from that of other forager societies in the higher age-specific fertility rates found in the two lower age classes. Future studies will need to assess whether this particular pattern and the short interbirth interval are related to highly cooperative childrearing, which in the Baka is associated with slow growth. The fertility rate has fallen drastically since 2011, and this matches the arrival of cheap alcohol in the community. Our data provide a first-hand record of the impact of alcohol on fertility in a hunter-gatherer society which appears to be seriously compromising the survival of the Baka.
Collapse
Affiliation(s)
- Fernando V Ramirez Rozzi
- UMR 5288 Laboratoire Anthropologie Moléculaire et Imagerie de Synthèse, CNRS, Faculté de Chirurgie Dentaire, 92120 Montrouge, France
| |
Collapse
|
16
|
Ross CT, Borgerhoff Mulder M, Oh SY, Bowles S, Beheim B, Bunce J, Caudell M, Clark G, Colleran H, Cortez C, Draper P, Greaves RD, Gurven M, Headland T, Headland J, Hill K, Hewlett B, Kaplan HS, Koster J, Kramer K, Marlowe F, McElreath R, Nolin D, Quinlan M, Quinlan R, Revilla-Minaya C, Scelza B, Schacht R, Shenk M, Uehara R, Voland E, Willführ K, Winterhalder B, Ziker J. Greater wealth inequality, less polygyny: rethinking the polygyny threshold model. J R Soc Interface 2018; 15:20180035. [PMID: 30021924 PMCID: PMC6073648 DOI: 10.1098/rsif.2018.0035] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2018] [Accepted: 06/25/2018] [Indexed: 11/12/2022] Open
Abstract
Monogamy appears to have become the predominant human mating system with the emergence of highly unequal agricultural populations that replaced relatively egalitarian horticultural populations, challenging the conventional idea-based on the polygyny threshold model-that polygyny should be positively associated with wealth inequality. To address this polygyny paradox, we generalize the standard polygyny threshold model to a mutual mate choice model predicting the fraction of women married polygynously. We then demonstrate two conditions that are jointly sufficient to make monogamy the predominant marriage form, even in highly unequal societies. We assess if these conditions are satisfied using individual-level data from 29 human populations. Our analysis shows that with the shift to stratified agricultural economies: (i) the population frequency of relatively poor individuals increased, increasing wealth inequality, but decreasing the frequency of individuals with sufficient wealth to secure polygynous marriage, and (ii) diminishing marginal fitness returns to additional wives prevent extremely wealthy men from obtaining as many wives as their relative wealth would otherwise predict. These conditions jointly lead to a high population-level frequency of monogamy.
Collapse
Affiliation(s)
- Cody T Ross
- Behavioral Sciences Program, Santa Fe Institute, Santa Fe, NM, USA
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | | | - Seung-Yun Oh
- Korea Insurance Research Institute, Yeongdeungpo-gu, Republic of Korea
| | - Samuel Bowles
- Behavioral Sciences Program, Santa Fe Institute, Santa Fe, NM, USA
| | - Bret Beheim
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - John Bunce
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - Mark Caudell
- Allen School for Global Animal Health, Washington State University, Pullman, WA, USA
| | - Gregory Clark
- Department of Anthropology, University of California, Davis, CA, USA
| | - Heidi Colleran
- Dept. of Linguistic and Cultural Evolution, Max Planck Institute for the Science of Human History, Leipzig, Germany
| | - Carmen Cortez
- Department of Anthropology, University of California, Davis, CA, USA
| | - Patricia Draper
- Department of Anthropology, University of Nebraska, Lincoln, NE, USA
| | | | - Michael Gurven
- Department of Anthropology, University of California, Santa Barbara, CA, USA
| | | | | | - Kim Hill
- School of Human Evolution and Social Change, Arizona State University, Tempe, AZ, USA
| | - Barry Hewlett
- Department of Anthropology, Washington State University, Vancouver, WA, USA
| | - Hillard S Kaplan
- Department of Anthropology, University of New Mexico, Albuquerque, NM, USA
| | - Jeremy Koster
- Department of Anthropology, University of Cincinnati, Cincinnati, OH, USA
| | - Karen Kramer
- Department of Anthropology, University of Utah, Logan, UT, USA
| | - Frank Marlowe
- Department of Biological Anthropology, University of Cambridge, UK
| | - Richard McElreath
- Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany
| | - David Nolin
- Department of Anthropology, Pennsylvania State University, Philadelphia, PA, USA
| | - Marsha Quinlan
- Department of Anthropology, Washington State University, Vancouver, WA, USA
| | - Robert Quinlan
- Department of Anthropology, Washington State University, Vancouver, WA, USA
| | | | - Brooke Scelza
- Department of Anthropology, University of California, Los Angeles, CA, USA
| | - Ryan Schacht
- Department of Anthropology, University of Utah, Logan, UT, USA
| | - Mary Shenk
- Department of Anthropology, Pennsylvania State University, Philadelphia, PA, USA
| | | | - Eckart Voland
- Institut für Philosophie der Universität Giessen, Giessen, Germany
| | - Kai Willführ
- Carl von Ossietzky University of Oldenburg, Oldenburg, Germany
| | | | - John Ziker
- Department of Anthropology, Boise State University, Boise, ID, USA
| |
Collapse
|
17
|
Judd MA, Walker JL, Ventresca Miller A, Razhev D, Epimakhov AV, Hanks BK. Life in the fast lane: Settled pastoralism in the Central Eurasian Steppe during the Middle Bronze Age. Am J Hum Biol 2018; 30:e23129. [DOI: 10.1002/ajhb.23129] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 01/16/2018] [Accepted: 03/16/2018] [Indexed: 01/01/2023] Open
Affiliation(s)
- Margaret A. Judd
- Department of Anthropology; University of Pittsburgh; Pittsburgh Pennsylvania 15260
| | - Jessica L. Walker
- Department of Anthropology; University of Pittsburgh; Pittsburgh Pennsylvania 15260
| | - Alicia Ventresca Miller
- Christian-Albrechts-Universität zu Kiel, Human Development in Landscapes, Institute for Prehistoric and Protohistoric Archaeology, Archaeological Stable Isotope Laboratory; Kiel, 24118 Germany
- Department of Archaeology; Max Planck Institute for the Science of Human History; Jena, 07745 Germany
| | - Dmitry Razhev
- Tyumen Scientific Centre SB RAS, Institute of the Problems of Northern Development; Tyumen Russia
| | - Andrey V. Epimakhov
- Institute of History and Archaeology (Ural Branch of the Russian Academy of Sciences); South Ural State University; Chelyabinsk, 454080 Russia
| | - Bryan K. Hanks
- Department of Anthropology; University of Pittsburgh; Pittsburgh Pennsylvania 15260
| |
Collapse
|
18
|
Urlacher SS, Kramer KL. Evidence for energetic tradeoffs between physical activity and childhood growth across the nutritional transition. Sci Rep 2018; 8:369. [PMID: 29321690 PMCID: PMC5762677 DOI: 10.1038/s41598-017-18738-4] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 12/15/2017] [Indexed: 12/17/2022] Open
Abstract
Despite broad implications for understanding human life history, energetics, and health, the impact of physical activity on childhood growth remains unclear. Particularly understudied is the effect of secular changes in physical activity on child development. We address these shortcomings using data spanning the transition from traditional to semi-developed economy among Yucatec Maya agriculturalists. Anthropometric and behavioral observation data were collected from children living in a subsistence-based rural community in 1992 and again in 2012 following the introduction of a school and mechanized technologies but minimal overt dietary change. Multiple regression analyses demonstrate dramatic twenty-year transformations in how children spent their time. This behavioral change was associated with large declines in estimated physical activity level (PAL), associated activity energy expenditure savings of several hundred kilocalories/day, and sizable increases in mean height, weight, and triceps skinfold thickness. Controlling for observed frequency of market food consumption, PAL was inversely related to child body size and subcutaneous fat stores and significantly mediated the effects of data collection year on anthropometric indices. These findings indicate that physical activity can considerably influence childhood growth, highlighting the role of energy allocation tradeoffs between physical activity and competing life tasks in shaping patterns of human ontogeny and health.
Collapse
Affiliation(s)
- Samuel S Urlacher
- Department of Anthropology, CUNY Hunter College, New York, NY, 10065, USA.
| | - Karen L Kramer
- Department of Anthropology, University of Utah, Salt Lake City, UT, 84112, USA
| |
Collapse
|
19
|
Longman D, Stock JT, Wells JCK. A trade-off between cognitive and physical performance, with relative preservation of brain function. Sci Rep 2017; 7:13709. [PMID: 29057922 PMCID: PMC5651807 DOI: 10.1038/s41598-017-14186-2] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2016] [Accepted: 09/19/2017] [Indexed: 01/08/2023] Open
Abstract
Debate surrounds the issue of how the large, metabolically expensive brains of Homo sapiens can be energetically afforded. At the evolutionary level, decreased investment in muscularity, adiposity and the digestive tract allow for a larger brain. Developmentally, high neo-natal adiposity and preferential distribution of resources to the brain provide an energetic buffer during times of environmental stress. Through an experimental design, we investigated the hypothesis of a trade-off involving brain and muscle at the acute level in humans. Mental performance was measured by a free-recall test, and physical performance by power output on an indoor rowing ergometer. Sixty-two male student rowers performed the two tests in isolation, and then again simultaneously. Paired samples t-tests revealed that both power output and mental performance reduced when tested together compared to in isolation (t(61) = 9.699, p < 0.001 and t(61) = 8.975, p < 0.001). Furthermore, the decrease in physical performance was greater than the decrease in mental performance (t(61) = -2.069, p = 0.043). This is the first investigation to demonstrate an acute level trade-off between these two functions, and provides support for the selfish brain hypothesis due to the relative preservation of cognitive function over physical power output. The underlying mechanism is unclear, and requires further work.
Collapse
Affiliation(s)
- Daniel Longman
- Department of Archaeology and Anthropology, University of Cambridge, Cambridge, CB2 3QG, UK.
| | - Jay T Stock
- Department of Archaeology and Anthropology, University of Cambridge, Cambridge, CB2 3QG, UK
- Department of Anthropology, University of Western Ontario, Ontario, Canada
| | - Jonathan C K Wells
- Childhood Nutrition Research Centre, UCL Institute of Child Health, London, WC1N 1EH, UK
| |
Collapse
|
20
|
Kramer KL, Schacht R, Bell A. Adult sex ratios and partner scarcity among hunter-gatherers: implications for dispersal patterns and the evolution of human sociality. Philos Trans R Soc Lond B Biol Sci 2017; 372:20160316. [PMID: 28760759 PMCID: PMC5540858 DOI: 10.1098/rstb.2016.0316] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/02/2017] [Indexed: 11/12/2022] Open
Abstract
Small populations are susceptible to high genetic loads and random fluctuations in birth and death rates. While these selective forces can adversely affect their viability, small populations persist across taxa. Here, we investigate the resilience of small groups to demographic uncertainty, and specifically to fluctuations in adult sex ratio (ASR), partner availability and dispersal patterns. Using 25 years of demographic data for two Savannah Pumé groups of South American hunter-gatherers, we show that in small human populations: (i) ASRs fluctuate substantially from year to year, but do not consistently trend in a sex-biased direction; (ii) the primary driver of local variation in partner availability is stochasticity in the sex ratio at maturity; and (iii) dispersal outside of the group is an important behavioural means to mediate locally constrained mating options. To then simulate conditions under which dispersal outside of the local group may have evolved, we develop two mathematical models. Model results predict that if the ASR is biased, the globally rarer sex should disperse. The model's utility is then evaluated by applying our empirical data to this central prediction. The results are consistent with the observed hunter-gatherer pattern of variation in the sex that disperses. Together, these findings offer an alternative explanation to resource provisioning for the evolution of traits central to human sociality (e.g. flexible dispersal, bilocal post-marital residence and cooperation across local groups). We argue that in small populations, looking outside of one's local group is necessary to find a mate and that, motivated by ASR imbalance, the alliances formed to facilitate the movement of partners are an important foundation for the human-typical pattern of network formation across local groups.This article is part of the themed issue 'Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'.
Collapse
Affiliation(s)
- Karen L Kramer
- Department of Anthropology, University of Utah, 270 South 1400 East, Room 102, Salt Lake City, UT 84112, USA
| | - Ryan Schacht
- Department of Anthropology, University of Utah, 270 South 1400 East, Room 102, Salt Lake City, UT 84112, USA
| | - Adrian Bell
- Department of Anthropology, University of Utah, 270 South 1400 East, Room 102, Salt Lake City, UT 84112, USA
| |
Collapse
|
21
|
Why does paternal death accelerate the transition to first marriage in the C18-C19 Krummhörn population? EVOL HUM BEHAV 2017. [DOI: 10.1016/j.evolhumbehav.2016.08.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
|
22
|
Amato KR. Incorporating the gut microbiota into models of human and non-human primate ecology and evolution. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2016; 159:S196-215. [PMID: 26808106 DOI: 10.1002/ajpa.22908] [Citation(s) in RCA: 52] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The mammalian gut is home to a diverse community of microbes. Advances in technology over the past two decades have allowed us to examine this community, the gut microbiota, in more detail, revealing a wide range of influences on host nutrition, health, and behavior. These host-gut microbe interactions appear to shape host plasticity and fitness in a variety of contexts, and therefore represent a key factor missing from existing models of human and non-human primate ecology and evolution. However, current studies of the gut microbiota tend to include limited contextual data or are clinical, making it difficult to directly test broad anthropological hypotheses. Here, I review what is known about the animal gut microbiota and provide examples of how gut microbiota research can be integrated into the study of human and non-human primate ecology and evolution with targeted data collection. Specifically, I examine how the gut microbiota may impact primate diet, energetics, disease resistance, and cognition. While gut microbiota research is proliferating rapidly, especially in the context of humans, there remain important gaps in our understanding of host-gut microbe interactions that will require an anthropological perspective to fill. Likewise, gut microbiota research will be an important tool for filling remaining gaps in anthropological research.
Collapse
|
23
|
Urlacher SS, Blackwell AD, Liebert MA, Madimenos FC, Cepon-Robins TJ, Gildner TE, Snodgrass JJ, Sugiyama LS. Physical growth of the shuar: Height, Weight, and BMI references for an indigenous amazonian population. Am J Hum Biol 2015; 28:16-30. [PMID: 26126793 DOI: 10.1002/ajhb.22747] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Revised: 05/04/2015] [Accepted: 05/15/2015] [Indexed: 01/22/2023] Open
Abstract
OBJECTIVES Information concerning physical growth among small-scale populations remains limited, yet such data are critical to local health efforts and to foster basic understandings of human life history and variation in childhood development. Using a large dataset and robust modeling methods, this study aims to describe growth from birth to adulthood among the indigenous Shuar of Amazonian Ecuador. METHODS Mixed-longitudinal measures of height, weight, and body mass index (BMI) were collected from Shuar participants (n = 2,463; age: 0-29 years). Centile growth curves and tables were created for each anthropometric variable of interest using Generalized Additive Models for Location, Scale, and Shape (GAMLSS). Pseudo-velocity and Lambda-Mu-Sigma curves were generated to further investigate Shuar patterns of growth and to facilitate comparison with United States Center for Disease Control and Prevention and multinational World Health Organization growth references. RESULTS The Shuar are small throughout life and exhibit complex patterns of growth that differ substantially from those of international references. Similar to other Amazonians, Shuar growth in weight compares more favorably to references than growth in height, resulting in BMI curves that approximate international medians. Several additional characteristics of Shuar development are noteworthy, including large observed variation in body size early in life, significant infant growth faltering, extended male growth into adulthood, and a markedly early female pubertal growth spurt in height. Phenotypic plasticity and genetic selection in response to local environmental factors may explain many of these patterns. CONCLUSIONS Providing a detailed reference of growth for the Shuar and other Amazonian populations, this study possesses direct clinical application and affords valuable insight into childhood health and the ecology of human growth.
Collapse
Affiliation(s)
- Samuel S Urlacher
- Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts, 02138
| | - Aaron D Blackwell
- Department of Anthropology, University of California, Santa Barbara, California, 93106.,Broom Center for Demography, University of California, Santa Barbara, California, 93106.,Center for Evolutionary Psychology, , University of California, Santa Barbara, California, 93106
| | - Melissa A Liebert
- Department of Anthropology, University of Oregon, Eugene, Oregon, 97403.,Institute of Cognitive and Decision Sciences, University of Oregon, Eugene, Oregon, 97403
| | | | - Tara J Cepon-Robins
- Department of Anthropology, University of Oregon, Eugene, Oregon, 97403.,Institute of Cognitive and Decision Sciences, University of Oregon, Eugene, Oregon, 97403
| | - Theresa E Gildner
- Department of Anthropology, University of Oregon, Eugene, Oregon, 97403.,Institute of Cognitive and Decision Sciences, University of Oregon, Eugene, Oregon, 97403
| | - J Josh Snodgrass
- Department of Anthropology, University of Oregon, Eugene, Oregon, 97403.,Institute of Cognitive and Decision Sciences, University of Oregon, Eugene, Oregon, 97403
| | - Lawrence S Sugiyama
- Broom Center for Demography, University of California, Santa Barbara, California, 93106.,Department of Anthropology, University of Oregon, Eugene, Oregon, 97403.,Institute of Cognitive and Decision Sciences, University of Oregon, Eugene, Oregon, 97403
| |
Collapse
|
24
|
Gurri FD, Ortega-Muñoz A. Impact of commercial farming on household reproductive strategies in Calakmul, Campeche, Mexico. Am J Hum Biol 2015; 27:758-66. [PMID: 26094716 DOI: 10.1002/ajhb.22753] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Revised: 04/28/2015] [Accepted: 05/16/2015] [Indexed: 11/10/2022] Open
Abstract
OBJECTIVES The purpose of this study was to determine if commercial agriculture can lead to changes in peasant reproductive strategies in migrant agriculturalists from Calakmul, Campeche, Mexico. METHODS The reproductive histories of 746 women from Calakmul, Campeche, Mexico were collected. The sample was first divided into women who had reproduced within or outside of Calakmul (RC and RO, respectively) and these were further subdivided into those who lived in households practicing subsistence agriculture and those who turned agriculture into a business (Household Subsistence Agricultural Strategy (HSA) and Household Commercial Agricultural Strategy (HCA), respectively). Age-specific fertility rate (ASFR) differences were compared between strategies and place of reproduction. Comparisons between interbirth interval and age at which desired fertility was reached were done with a Kaplan-Meier life table-based statistic. RESULTS In both strategies, RC women increased ASFRs by reducing age at first birth, and HSA-RC women also reduced interbirth intervals. HCA women had lower ASFRs than HSA women. The latter had a natural fertility pattern while the former expressed a desire to stop reproducing at a younger age. HCA-RC women showed important fertility reductions after age 25 and HCA-RO women after age 30. CONCLUSIONS Fertility reductions in households that practice commercial versus those that practice subsistence agriculture were significant. Also, a "frontier" effect was observed that increased fertility over all, but HCA households were not as influenced by it.
Collapse
Affiliation(s)
- Francisco D Gurri
- Department of Sustainability Science, El Colegio de la Frontera Sur (ECOSUR), Lerma Campeche, Campeche, C.P. 24500, Mexico
| | - Allan Ortega-Muñoz
- Centro INAH Quintana Roo, Av. Insurgentes #974 Col Forjadores, Chetumal, Quintana Roo, C.P. 77025, Mexico
| |
Collapse
|
25
|
Affiliation(s)
- Tanya M. Smith
- Department of Human Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138;
| |
Collapse
|
26
|
Rind B. Critique of Hames and Blanchard (2012), Clancy (2012), and Ryniker (2012) on hebephilia, anthropological data, and maladaptiveness. ARCHIVES OF SEXUAL BEHAVIOR 2013; 42:685-691. [PMID: 23760771 DOI: 10.1007/s10508-013-0132-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
|
27
|
Reiches MW, Moore SE, Prentice AM, Prentice A, Sawo Y, Ellison PT. The adolescent transition under energetic stress: Body composition tradeoffs among adolescent women in The Gambia. EVOLUTION MEDICINE AND PUBLIC HEALTH 2013; 2013:75-85. [PMID: 24481188 PMCID: PMC3868354 DOI: 10.1093/emph/eot005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
BACKGROUND AND OBJECTIVES Life history theory predicts a shift in energy allocation from growth to reproductive function as a consequence of puberty. During adolescence, linear growth tapers off and, in females, ovarian steroid production increases. In this model, acquisition of lean mass is associated with growth while investment in adiposity is associated with reproduction. This study examines the chronological and developmental predictors of energy allocation patterns among adolescent women under conditions of energy constraint. METHODOLOGY Fifty post-menarcheal adolescent women between 14 and 20 years old were sampled for weight and body composition at the beginning and end of 1 month in an energy-adequate season and 1 month in the subsequent energy-constrained season in a rural province of The Gambia. RESULTS Chronologically and developmentally younger adolescent girls gain weight in the form of lean mass in both energy-adequate and energy-constrained seasons, whereas older adolescents lose lean mass under conditions of energetic stress (generalized estimating equation (GEE) Wald chi-square comparing youngest tertile with older two tertiles 9.750, P = 0.002; GEE Wald chi-square comparing fast- with slow-growing individuals for growth rate 19.806, P < 0.001). When energy is limited, younger adolescents lose and older adolescents maintain fat (GEE Wald chi-square for interaction of age and season 6.568, P = 0.010; GEE Wald chi-square comparing fast- with slow-growing individuals for interaction of growth rate and season 7.807, P = 0.005). CONCLUSIONS AND IMPLICATIONS When energy is constrained, the physiology of younger adolescents invests in growth while that of older adolescent females privileges reproductively valuable adipose tissue.
Collapse
Affiliation(s)
- Meredith W Reiches
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA, USA; MRC Keneba, MRC Unit, The Gambia; MRC International Nutrition Group, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK; and MRC Human Nutrition Research, Elsie Widdowson Laboratory, Cambridge, CB1 9NL, UK
| | | | | | | | | | | |
Collapse
|
28
|
Meehan CL, Quinlan R, Malcom CD. Cooperative breeding and maternal energy expenditure among Aka foragers. Am J Hum Biol 2012. [PMID: 23203600 DOI: 10.1002/ajhb.22336] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
OBJECTIVES Previous research among foragers and theory suggests that nonmaternal caregivers offer essential assistance, which supports female reproduction and the costs associated with lengthy child development. Mothers' face trade-offs in energy allocation between work and childcare, particularly when mothers have an infant. These trade-offs likely have crucial impacts on the pace of reproduction and child health. Caregivers can help mothers with childcare or they can reduce a mother's nonchildcare workload. If caregivers assist mothers by substituting childcare, then maternal energy expenditure (EE) in other work activities should increase. If caregivers assist mothers by substituting labor, then maternal EE in work activities should decrease when caregivers are present. METHODS Utilizing detailed, quantitative behavioral observations and EE data, we test these propositions with data from 28 Aka forager mothers with children <35 months old. We isolate paternal, grandmaternal, and other caregiver effects on maternal EE and childcare in multivariate analyses. RESULTS Our results show that caregivers (largely grandmothers) significantly reduce mothers' work EE by as much 216 kcal across a 9-hour observation period, while fathers and juveniles appear to increase maternal EE. Direct childcare from grandmothers decreases maternal direct care by about one-to-one indicating a labor substitution. Direct childcare from fathers decreases maternal care by almost 4 to 1, resulting in a net reduction of total direct care from all caregivers. CONCLUSIONS Our results indicate that there are multiple pathways by which helpers offset maternal work/childcare trade-offs.
Collapse
Affiliation(s)
- Courtney L Meehan
- Department of Anthropology, Washington State University, Pullman, Washington 99164-4910, USA.
| | | | | |
Collapse
|
29
|
Veile A, Winking J, Gurven M, Greaves RD, Kramer KL. Infant growth and the thymus: data from two South American native societies. Am J Hum Biol 2012; 24:768-75. [PMID: 22915311 DOI: 10.1002/ajhb.22314] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Revised: 03/31/2012] [Accepted: 07/16/2012] [Indexed: 11/11/2022] Open
Abstract
The thymus plays an important role in the development of the immune system, yet little is known about the patterns and sources of variation in postnatal thymic development. The aim of this study is to contribute cross-cultural data on thymus size in infants from two South American native populations, the Tsimane of Bolivia and the Pumé of Venezuela. Thymic ultrasonography was performed and standard anthropometric measures collected from 86 Tsimane and Pumé infants. Patterns of infant growth and thymus size were compared between the two populations and the relationship between nutritional status and thymus size was assessed. Despite nearly identical anthropometric trajectories, Tsimane infants had larger thymuses than Pumé infants at all ages. Population, infant age, and infant mid-upper arm circumference were significant predictors of thymus area in the Tsimane and Pumé infants. This finding reveals a cross-cultural difference in thymus size that is not driven by nutritional status. We suggest that future studies focus on isolating prenatal and postnatal environmental factors underlying cross-cultural variation in thymic development.
Collapse
Affiliation(s)
- Amanda Veile
- Department of Human Evolutionary Biology, Harvard University, Cambridge Massachusetts 02138, USA.
| | | | | | | | | |
Collapse
|
30
|
Leonard WR. Laboratory and field methods for measuring human energy expenditure. Am J Hum Biol 2012; 24:372-84. [PMID: 22419374 DOI: 10.1002/ajhb.22260] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2012] [Revised: 02/01/2012] [Accepted: 02/05/2012] [Indexed: 01/10/2023] Open
Abstract
Energetics research is central to the field of human biology. Energy is an important currency for measuring adaptation, because both its acquisition and allocation for biological processes have important implications for survival and reproduction. Recent technological and methodological advances are now allowing human biologists to study variation in energy dynamics with much greater accuracy in a wide variety of ecological contexts. This article provides an overview of the methods used for measuring human energy expenditure (EE) and considers some of the important ecological and evolutionary questions that can be explored from an energetics perspective. Basic principles of calorimetry are first presented, followed by an overview of the equipment used for measuring human EE and work capacity. Methods for measuring three important dimensions of human EE-resting metabolic rate, working/exercising EE, and total EE-are then presented, highlighting key areas of ongoing research.
Collapse
Affiliation(s)
- William R Leonard
- Laboratory for Human Biology Research, Department of Anthropology, Northwestern University, Evanston, Illinois, USA.
| |
Collapse
|
31
|
Abstract
Primates are characterized by relatively late ages at first reproduction, long lives and low fertility. Together, these traits define a life-history of reduced reproductive effort. Understanding the optimal allocation of reproductive effort, and specifically reduced reproductive effort, has been one of the key problems motivating the development of life-history theory. Because of their unusual constellation of life-history traits, primates play an important role in the continued development of life-history theory. In this review, I present the evidence for the reduced reproductive effort life histories of primates and discuss the ways that such life-history tactics are understood in contemporary theory. Such tactics are particularly consistent with the predictions of stochastic demographic models, suggesting a key role for environmental variability in the evolution of primate life histories. The tendency for primates to specialize in high-quality, high-variability food items may make them particularly susceptible to environmental variability and explains their low reproductive-effort tactics. I discuss recent applications of life-history theory to human evolution and emphasize the continuity between models used to explain peculiarities of human reproduction and senescence with the long, slow life histories of primates more generally.
Collapse
Affiliation(s)
- James Holland Jones
- Department of Anthropology, Woods Institute for the Environment, Stanford University 450 Serra Mall, Building 50, Stanford, CA 94305-2034, USA.
| |
Collapse
|
32
|
Juvenile Subsistence Effort, Activity Levels, and Growth Patterns. HUMAN NATURE-AN INTERDISCIPLINARY BIOSOCIAL PERSPECTIVE 2011; 22:303-26. [DOI: 10.1007/s12110-011-9122-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
33
|
Kramer KL, Greaves RD. Postmarital Residence and Bilateral Kin Associations among Hunter-Gatherers. HUMAN NATURE-AN INTERDISCIPLINARY BIOSOCIAL PERSPECTIVE 2011; 22:41-63. [DOI: 10.1007/s12110-011-9115-7] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
|
34
|
Abstract
Teen motherhood is the prevalent childbearing pattern in most traditional populations. Yet early motherhood is associated with negative biological and social outcomes in the developed world. We review the teen pregnancy literature in light of this discrepancy, emphasizing two core debates. The first debate centers on whether teens have poor pregnancy outcomes compared to older women, and whether negative outcomes are biologically based. Second, we consider the debate over the confounding effects of socio-economic conditions associated with being young. When teens are considered as a group, results are inconsistent across studies. When teens are disaggregated by age, the strongest finding across studies is that biological risk is concentrated in only the youngest of mothers. Negative consequences are associated with teen motherhood not because of chronological age per se, but because of relative developmental maturity and the availability of non-maternal support. In most traditional societies as well as in some sectors of developed societies, teen motherhood occurs within the context of extended kin networks and is subsidized through reliable economic and childcare assistance. Child-rearing practices, rather than pregnancy per se, may explain much of the discrepancy in the prevalence, success and attitudes toward teen motherhood in traditional and developed societies.
Collapse
Affiliation(s)
- Karen L Kramer
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
| | | |
Collapse
|
35
|
Sloboda DM, Hickey M, Hart R. Reproduction in females: the role of the early life environment. Hum Reprod Update 2010; 17:210-27. [DOI: 10.1093/humupd/dmq048] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
|
36
|
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]
|
37
|
Decaro JA, Decaro E, Worthman CM. Sex differences in child nutritional and immunological status 5-9 years post contact in fringe highland Papua New Guinea. Am J Hum Biol 2010; 22:657-66. [DOI: 10.1002/ajhb.21062] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
|
38
|
Kramer KL, Greaves RD. Synchrony between growth and reproductive patterns in human females: Early investment in growth among Pumé foragers. AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2010; 141:235-44. [PMID: 19844999 DOI: 10.1002/ajpa.21139] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Life history is an important framework for understanding many aspects of ontogeny and reproduction relative to fitness outcomes. Because growth is a key influence on the timing of reproductive maturity and age at first birth is a critical demographic variable predicting lifetime fertility, it raises questions about the synchrony of growth and reproductive strategies. Among the Pumé, a group of South American foragers, young women give birth to their first child on average at age 15.5. Previous research showed that this early age at first birth maximizes surviving fertility under conditions of high infant mortality. In this study we evaluate Pumé growth data to test the expectation that if early reproduction is advantageous, then girls should have a developmental trajectory that best prepares them for young childbearing. Analyses show that comparatively Pumé girls invest in skeletal growth early, enter puberty having achieved a greater proportion of adult body size and grow at low velocities during adolescence. For early reproducers growing up in a food-limited environment, a precocious investment in growth is advantageous because juveniles have no chance of pregnancy and it occurs before the onset of the competing metabolic demands of final reproductive maturation and childbearing. Documenting growth patterns under preindustrial energetic and demographic conditions expands the range of developmental variation not otherwise captured by normative growth standards and contributes to research on human phenotypic plasticity in diverse environments.
Collapse
Affiliation(s)
- Karen L Kramer
- Department of Anthropology, Harvard University, Cambridge, MA 02138, USA.
| | | |
Collapse
|
39
|
Sear R, Gibson M. Introduction to special issue on "Trade-Offs in Female Life Histories: Integrating Evolutionary Frameworks". Am J Hum Biol 2009; 21:417-20. [PMID: 19418528 DOI: 10.1002/ajhb.20952] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Affiliation(s)
- Rebecca Sear
- Department of Social Policy, London School of Economics, United Kingdom
| | | |
Collapse
|