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Lewis ME, French JC, Rossoni-Notter E, Notter O, Moussous A, Sparacello V, Boschin F, Ricci S, Nowell A. An assessment of puberty status in adolescents from the European Upper Paleolithic. J Hum Evol 2024:103577. [PMID: 39266410 DOI: 10.1016/j.jhevol.2024.103577] [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: 03/20/2024] [Revised: 07/26/2024] [Accepted: 07/26/2024] [Indexed: 09/14/2024]
Abstract
Childhood and adolescence are two life-history stages that are either unique to humans, or significantly expanded in the human life course relative to other primates. While recent studies have deepened our knowledge of childhood in the Upper Paleolithic, adolescence in this period remains understudied. Here, we use bioarchaeological maturational markers to estimate puberty status of 13 Upper Paleolithic adolescents from sites in Russia, Czechia, and Italy to 1) evaluate the feasibility of the application of bioarchaeological puberty assessment methods to Upper Paleolithic (Homo sapiens) skeletal individuals, 2) estimate the timing and tempo of puberty in Upper Paleolithic adolescents compared to other archaeological populations analyzed using the same method, and 3) characterize adolescence in the Upper Paleolithic by contextualizing the results of this puberty assessment with data on individual and population-level health, morbidity and burial practices. Our results revealed that while puberty had begun by 13.5 years of age for the majority of individuals, there was a lot of variability, with the adolescents from Arene Candide (AC1 and AC16), both aged around 16 years when they died, taking several years longer to progress through puberty than their peers. Assessing the age of menarche was challenging due to the paucity of female adolescents, but based on the available evidence, it appears to have occurred between 16 and 17 years of age. For some, full adulthood had been achieved by 17-22 years, similar to the patterns seen in modern wealthy countries and in advance of historic populations living in urbanized environments. The bioarchaeological analysis of puberty among Upper Paleolithic adolescents has important implications for the study of the emergence of adolescence within human-life histories, as well as for understanding the developmental plasticity of sexual maturation across past and present human populations.
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Affiliation(s)
- Mary E Lewis
- Department of Archaeology, University of Reading, Reading, RG6 6NZ, UK
| | - Jennifer C French
- Department of Archaeology, Classics and Egyptology, 12-14 Abercromby Square, University of Liverpool, Liverpool, L69 7WZ, UK
| | - Elena Rossoni-Notter
- Museum of Prehistoric Anthropology of Monaco, 56 bis Boulevard du Jardin Exotique, 98000, Monaco
| | - Olivier Notter
- Museum of Prehistoric Anthropology of Monaco, 56 bis Boulevard du Jardin Exotique, 98000, Monaco
| | - Abdelkader Moussous
- Museum of Prehistoric Anthropology of Monaco, 56 bis Boulevard du Jardin Exotique, 98000, Monaco
| | - Vitale Sparacello
- Department of Life and Environmental Sciences, University of Cagliari, Cittadella Monserrato, Cagliari, Italy
| | - Francesco Boschin
- University of Siena, Department of Physical Sciences, Earth and Environment, Via Laterina 8, 53100, Siena, Italy
| | - Stefano Ricci
- University of Siena, Department of Physical Sciences, Earth and Environment, Via Laterina 8, 53100, Siena, Italy
| | - April Nowell
- Department of Anthropology, University of Victoria, Cornett Building Room B228, 3800 Finnerty Road, Victoria, BC, V8P 5C2, Canada.
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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'.
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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
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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.
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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
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Childhood Teaching and Learning among Savanna Pumé Hunter-Gatherers. HUMAN NATURE-AN INTERDISCIPLINARY BIOSOCIAL PERSPECTIVE 2021; 32:87-114. [DOI: 10.1007/s12110-021-09392-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/25/2021] [Indexed: 12/25/2022]
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Abstract
For girls and women, marriage under 18 years is commonplace in many low-income nations today and was culturally widespread historically. Global health campaigns refer to marriage below this threshold as ‘child marriage’ and increasingly aim for its universal eradication, citing its apparent negative wellbeing consequences. Here, we outline and evaluate four alternative hypotheses for the persistence of early marriage, despite its associations with poor wellbeing, arising from the theoretical framework of human behavioral ecology. First, early marriage may be adaptive (e.g., it maximizes reproductive success), even if detrimental to wellbeing, when life expectancy is short. Second, parent–offspring conflict may explain early marriage, with parents profiting economically at the expense of their daughter’s best interests. Third, early marriage may be explained by intergenerational conflict, whereby girls marry young to emancipate themselves from continued labor within natal households. Finally, both daughters and parents from relatively disadvantaged backgrounds favor early marriage as a ‘best of a bad job strategy’ when it represents the best option given a lack of feasible alternatives. The explanatory power of each hypothesis is context-dependent, highlighting the complex drivers of life history transitions and reinforcing the need for context-specific policies addressing the vulnerabilities of adolescence worldwide.
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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.
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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
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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]
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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.
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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
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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.
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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
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10
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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]
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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.
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Affiliation(s)
- Fernando V Ramirez Rozzi
- UMR 5288 Laboratoire Anthropologie Moléculaire et Imagerie de Synthèse, CNRS, Faculté de Chirurgie Dentaire, 92120 Montrouge, France
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12
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Veile A. Hunter-gatherer diets and human behavioral evolution. Physiol Behav 2018; 193:190-195. [PMID: 29800635 DOI: 10.1016/j.physbeh.2018.05.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Revised: 05/15/2018] [Accepted: 05/15/2018] [Indexed: 11/30/2022]
Abstract
Human behavior and physiology evolved under conditions vastly different from those which most humans inhabit today. This paper summarizes long-term dietary studies conducted on contemporary hunter-gatherer populations (sometimes referred to as foragers). Selected studies for the most part that use evolutionary theoretical perspectives and data collection methods derived from the academic field of human behavioral ecology, which derives relatively recently from the fields of evolutionary biology, ethology, population biology and ecological anthropology. I demonstrate how this body of research illuminates ancestral patterns of food production, consumption and sharing, infant feeding, and juvenile subsistence contributions in hunter-gatherer economies. Insights from hunter-gatherer studies are then briefly discussed within the context of better-studied human populations that are Westernized, Educated, Industrialized, Rich, and Democratic (WEIRD).
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Affiliation(s)
- Amanda Veile
- Department of Anthropology, Purdue University, USA; Center on Aging and the Life Course, Purdue University, USA.
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Kramer KL, Veile A. Infant allocare in traditional societies. Physiol Behav 2018; 193:117-126. [PMID: 29730035 DOI: 10.1016/j.physbeh.2018.02.054] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2017] [Revised: 02/28/2018] [Accepted: 02/28/2018] [Indexed: 11/17/2022]
Abstract
Across human societies infants receive care from both their mothers and others. Reproductive cooperation raises two important questions: how does allocare benefit mothers and infants, and why do caretakers help mothers when they could spend their time in other, perhaps more valuable ways? We use behavioral and biological data from three small-scale societies to evaluate 1) how allocare affects a nursing mother's time, 2) whether a mother's birth interval length, surviving fertility and infant weight vary as a function of the childcare help that she receives, and 3) the opportunity cost for helpers to spend time caring for children. Across our hunter-gatherer and agricultural samples we find that on average mothers provide 57% of the direct care that an infant receives and allocaretakers 43% (±20%). Model results show that for every 10% increase in allocare the probability that a mother engages in direct care diminishes by 25%, a potential savings of an estimated 165 kcals per day. While allocare has a significant immediate impact on mother's time, no detectable effect on delayed fitness measures (birth interval and surviving fertility) or on infant weight status was evident. Cross culturally we find that other than mothers, siblings spend the most time caretaking infants, and they do so without compromising the time that they might otherwise spend in play, economic activities or education. The low opportunity cost for children to help offers an alternative explanation why juveniles are common caretakers in many societies, even in the absence of delayed indirect fitness benefits. While we expect specific patterns to vary cross culturally, these results point to the importance of infant allocare and its immediate time benefits for mothers to maintain flexibility in balancing the competing demands to support both older and younger children.
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Affiliation(s)
- Karen L Kramer
- Department of Anthropology, University of Utah, United States.
| | - Amanda Veile
- Department of Anthropology, Purdue University, United States
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Pittet F, Johnson C, Hinde K. Age at reproductive debut: Developmental predictors and consequences for lactation, infant mass, and subsequent reproduction in rhesus macaques (Macaca mulatta). AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 2017; 164:457-476. [PMID: 28895116 PMCID: PMC5759967 DOI: 10.1002/ajpa.23286] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2016] [Revised: 07/11/2017] [Accepted: 07/12/2017] [Indexed: 11/07/2022]
Abstract
OBJECTIVES The age at which females initiate their reproductive career is a critical life-history parameter with potential consequences on their residual reproductive value and lifetime fitness. The age at reproductive debut may be intimately tied to the somatic capacity of the mother to rear her young, but relatively little is known about the influence of age of first birth on milk synthesis within a broader framework of reproductive scheduling, infant outcomes, and other life-history tradeoffs. MATERIAL AND METHODS Our study investigated the predictors of age at first reproduction among 108 captive rhesus macaque (Macaca mulatta) females, and associations with their milk synthesis at peak lactation, infant mass, and ability to subsequently conceive and reproduce. RESULTS The majority of females reproduced in their fourth year (typical breeders); far fewer initiated their reproductive career one year earlier or one year later (respectively early and late breeders). Early breeders (3-year-old) benefited from highly favorable early life development (better juvenile growth, high dominance rank) to accelerate reproduction, but were impaired in milk synthesis due to lower somatic resources and their own continued growth. Comparatively, late breeders suffered from poor developmental conditions, only partially compensated by their delayed reproduction, and evinced compromised milk synthesis. Typical breeders not only produced higher available milk energy but also had best reproductive performance during the breeding and birth seasons following primiparity. DISCUSSION Here, we refine and extend our understanding of how life-history tradeoffs manifest in the magnitude, sources, and consequences of variation in age of reproductive debut. These findings provide insight into primate reproductive flexibility in the context of constraints and opportunities.
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Affiliation(s)
- Florent Pittet
- Brain, Mind, and Behavior Unit, California National Primate Research Center
- Center for Evolution and Medicine, Arizona State University
- School for Human Evolution and Social Change, Arizona State University
| | | | - Katie Hinde
- Brain, Mind, and Behavior Unit, California National Primate Research Center
- Center for Evolution and Medicine, Arizona State University
- School for Human Evolution and Social Change, Arizona State University
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15
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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'.
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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
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McKerracher L, Collard M, Altman R, Richards M, Nepomnaschy P. The ex-pat effect: presence of recent Western immigrants is associated with changes in age at first birth and birth rate in a Maya population from rural Guatemala. Ann Hum Biol 2017. [PMID: 28625087 DOI: 10.1080/03014460.2017.1343385] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
BACKGROUND Economic transitions expose indigenous populations to a variety of ecological and cultural challenges, especially regarding diet and stress. These kinds of challenges are predicted by evolutionary ecological theory to have fitness consequences (differential reproduction) and, indeed, are often associated with changes in fertility dynamics. It is currently unclear whether international immigration might impact the nature of such an economic transition or its consequences for fertility. AIM To examine measures of fertility, diet and stress in two economically transitioning Maya villages in Guatemala that have been differentially exposed to immigration by Westerners. SUBJECTS AND METHODS This study compared Maya women's ages at first birth and birth rates between villages and investigated whether these fertility indicators changed through time. It also explored whether the villages differed in relation to diet and/or a proxy of stress. RESULTS It was found that, in the village directly impacted by immigration, first births occurred earlier, but birth rate was slower. In both villages, over the sampled time window, age at first birth increased, while birth rate decreased. The villages do not differ significantly in dietary indicators, but the immigration-affected village scored higher on the stress proxy. CONCLUSION Immigration can affect fertility in host communities. This relationship between immigration and fertility dynamics may be partly attributable to stress, but this possibility should be evaluated prospectively in future research.
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Affiliation(s)
| | - Mark Collard
- a Department of Archaeology , Simon Fraser University , Burnaby , BC , Canada.,b Department of Archaeology , University of Aberdeen, King's College , Aberdeen , Scotland
| | - Rachel Altman
- c Department of Statistics and Actuarial Science , Simon Fraser University , Burnaby , BC , Canada
| | - Michael Richards
- a Department of Archaeology , Simon Fraser University , Burnaby , BC , Canada
| | - Pablo Nepomnaschy
- d Faculty of Health Sciences , Simon Fraser University , Burnaby , BC , Canada
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Seto MC. The Puzzle of Male Chronophilias. ARCHIVES OF SEXUAL BEHAVIOR 2017; 46:3-22. [PMID: 27549306 DOI: 10.1007/s10508-016-0799-y] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 06/15/2016] [Accepted: 06/22/2016] [Indexed: 05/24/2023]
Abstract
In this article, I return to the idea that pedophilia, a sexual interest in prepubescent children, can be considered a sexual orientation for age, in conjunction with the much more widely acknowledged and discussed sexual orientation for gender. Here, I broaden the scope to consider other chronophilias, referring to paraphilias for age/maturity categories other than young sexually mature adults. The puzzle of chronophilias includes questions about etiology and course, how chronophilias are related to each other, and what they can tell us about how human (male) sexuality is organized. In this article, I briefly review research on nepiophilia (infant/toddlers), pedophilia (prepubescent children), hebephilia (pubescent children), ephebophilia (postpubescent, sexually maturing adolescents), teleiophilia (young sexually mature adults, typically 20s and 30s), mesophilia (middle-aged adults, typically 40s and 50s), and gerontophilia (elderly adults, typically 60s and older) in the context of a multidimensional sexual orientations framework. Relevant research, limitations, and testable hypotheses for future work are identified.
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Affiliation(s)
- Michael C Seto
- Royal Ottawa Health Care Group, Ottawa, ON, K1Z 7K4, Canada.
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Rind B. Hebephilia and Other Chronophilic Puzzles. ARCHIVES OF SEXUAL BEHAVIOR 2017; 46:47-51. [PMID: 27815644 DOI: 10.1007/s10508-016-0889-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 10/19/2016] [Indexed: 06/06/2023]
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Hames R, Blanchard R. Postscript to "anthropological data regarding the adaptiveness of Hebephilia". ARCHIVES OF SEXUAL BEHAVIOR 2015; 44:13. [PMID: 23716200 DOI: 10.1007/s10508-013-0138-5] [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]
Affiliation(s)
- Raymond Hames
- Department of Anthropology, University of Nebraska, Lincoln, Lincoln, NE, 68588, USA,
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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]
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Gillespie DOS, Russell AF, Lummaa V. The effect of maternal age and reproductive history on offspring survival and lifetime reproduction in preindustrial humans. Evolution 2013; 67:1964-74. [PMID: 23815653 DOI: 10.1111/evo.12078] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Accepted: 01/30/2013] [Indexed: 02/03/2023]
Abstract
Senescence is one of the least understood aspects of organism life history. In part, this stems from the relatively late advent of complete individual-level datasets and appropriate statistical tools. In addition, selection against senescence should depend on the contribution to population growth arising from physiological investment in offspring at given ages, but offspring are rarely tracked over their entire lives. Here, we use a multigenerational dataset of preindustrial (1732-1860) Finns to describe the association of maternal age at offspring birth with offspring survival and lifetime reproduction. We then conduct longitudinal analyses to understand the drivers of this association. At the population level, offspring lifetime reproductive success (LRS) declined by 22% and individual λ, which falls with delays to reproduction, declined by 45% as maternal age at offspring birth increased from 16 to 50 years. These results were mediated by within-mother declines in offspring survival and lifetime reproduction. We also found evidence for modifying effects of offspring sex and maternal socioeconomic status. We suggest that our results emerge from the interaction of physiological with social drivers of offspring LRS, which further weakens selection on late-age reproduction and potentially molds the rate of senescence in humans.
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Affiliation(s)
- Duncan O S Gillespie
- Department of Animal & Plant Sciences, University of Sheffield, Sheffield, S10 2TN, UK.
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Gillette MT, Folinsbee KE. Early Menarche as an Alternative Reproductive Tactic in Human Females: An Evolutionary Approach to Reproductive Health Issues. EVOLUTIONARY PSYCHOLOGY 2012. [DOI: 10.1177/147470491201000506] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
The age at which a female reaches sexual maturity is critical in determining her future reproductive health and success. Thus, a worldwide decline in menarcheal age (timing of first menstrual period) may have serious long-term consequences. Early menarcheal timing (first menstrual period before age 12) can have a negative effect on fecundity, as well as the quality and quantity of offspring, and may consequently influence population growth or decline. In this paper, we apply an evolutionary framework to modern human health, and assess both proximate and ultimate consequences of declining menarcheal age. Examination of human reproductive health within an evolutionary framework is innovative and essential, because it illuminates the ultimate consequences of a declining age of menarche and facilitates new ways of thinking about the long-term and intergenerational transmission of health and disease; thus, an evolutionary framework lends itself to innovative public health and policy programs. In this paper, we examine whether or not early menarche is an alternative reproductive tactic that modern human females employ in response to a stressful environment, and whether or not early menarche is ultimately beneficial.
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Affiliation(s)
- Meghan T. Gillette
- Department of Human Development and Family Studies, Iowa State University, Ames, Iowa, USA
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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.
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Affiliation(s)
- Amanda Veile
- Department of Human Evolutionary Biology, Harvard University, Cambridge Massachusetts 02138, USA.
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Hames R, Blanchard R. Anthropological data regarding the adaptiveness of hebephilia. ARCHIVES OF SEXUAL BEHAVIOR 2012; 41:745-747. [PMID: 22644593 DOI: 10.1007/s10508-012-9972-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
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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]
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Hochberg Z, Gawlik A, Walker RS. Evolutionary fitness as a function of pubertal age in 22 subsistence-based traditional societies. INTERNATIONAL JOURNAL OF PEDIATRIC ENDOCRINOLOGY 2011; 2011:2. [PMID: 21860629 PMCID: PMC3159136 DOI: 10.1186/1687-9856-2011-2] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 06/21/2011] [Indexed: 11/25/2022]
Abstract
Context The age of puberty has fallen over the past 130 years in industrialized, western countries, and this fall is widely referred to as the secular trend for earlier puberty. The current study was undertaken to test two evolutionary theories: (a) the reproductive system maximizes the number of offspring in response to positive environmental cues in terms of energy balance, and (b) early puberty is a trade-off response for high mortality rate and reduced resource availability. Methods Using a sample of 22 natural-fertility societies of mostly tropical foragers, horticulturalists, and pastoralists from Africa, South America, Australia, and Southeastern Asia, this study compares indices of adolescence growth and menarche with those of fertility fitness in these non-industrial, traditional societies. Results The average age at menarche correlated with the first reproduction, but did not correlate with the total fertility rate TFR or reproductive fitness. The age at menarche correlated negatively with their average adult body mass, and the average adult body weight positively correlated with reproductive fitness. Survivorship did not correlate with the age at menarche or age indices of the adolescent growth spurt. The population density correlated positively with the age at first reproduction, but not with menarche age, TFR, or reproductive fitness. Conclusions Based on our analyses, we reject the working hypotheses that reproductive fitness is enhanced in societies with early puberty or that early menarche is an adaptive response to greater mortality risk. Whereas body mass is a measure of resources is tightly associated with fitness, the age of menarche is not.
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Affiliation(s)
- Ze'ev Hochberg
- Division of Pediatric Endocrinology, Meyer Children's Hospital, Rambam Medical Center, and Rappaport Faculty of Medicine and Research Institute, Technion-Israel Institute of Technology, Haifa, Israel
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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]
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Reported early family environment covaries with menarcheal age as a function of polymorphic variation in estrogen receptor-α. Dev Psychopathol 2011; 23:69-83. [PMID: 21262040 DOI: 10.1017/s0954579410000659] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Age at menarche, a sentinel index of pubertal maturation, was examined in relation to early family relationships (conflict, cohesion) and polymorphic variation in the gene encoding estrogen receptor-α (ESR1) in a midlife sample of 455 European American women. Consistent with prior literature, women who reported being raised in families characterized by close interpersonal relationships and little conflict tended to reach menarche at a later age than participants reared in families lacking cohesion and prone to discord. Moreover, this association was moderated by ESR1 variation, such that quality of the family environment covaried positively with menarcheal age among participants homozygous for minor alleles of the two ESR1 polymorphisms studied here (rs9304799, rs2234693), but not among women of other ESR1 genotypes. In addition, (a) family relationship variables were unrelated to ESR1 variation, and (b) genotype-dependent effects of childhood environment on age at menarche could not be accounted for by personality traits elsewhere shown to explain heritable variation in reported family conflict and cohesion. These findings are consistent with theories of differential susceptibility to environmental influence, as well as the more specific hypothesis (by Belsky) that girls differ genetically in their sensitivity to rearing effects on pubertal maturation.
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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.
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Affiliation(s)
- Karen L Kramer
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA.
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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.
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Affiliation(s)
- Karen L Kramer
- Department of Anthropology, Harvard University, Cambridge, MA 02138, USA.
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Coall DA, Chisholm JS. Reproductive development and parental investment during pregnancy: moderating influence of mother's early environment. Am J Hum Biol 2010; 22:143-53. [PMID: 19536836 DOI: 10.1002/ajhb.20965] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The association between a woman's age at menarche and the birth weight of her children is highly variable across human populations. Life history theory proposes that a woman's early environment may moderate this association and thus account for some of the variation between populations. According to one life history theory model, for individuals who develop in a childhood environment of high local mortality rates (experienced subjectively as psychosocial stress), it can be adaptive to mature earlier, have more offspring during their reproductive lifetime, and reduce investment in each offspring. In an environment of low psychosocial stress, however, it may be adaptive to mature later, have fewer offspring, and invest more in each. In this study, birth weight and proportionate birth weight (neonate's birth weight as a percentage of its mother's prepregnancy weight) were used as measures of parental investment during pregnancy. In a sample of 580 first-time mothers, we tested the hypothesis that the psychosocial stress experienced as a child would moderate the association between age at menarche and investment during pregnancy. We found that earlier menarche in those women who experienced stressful life events before 15 years of age was associated with a lower birth weight and proportionate birth weight. Conversely, in those who reported no childhood stressors, earlier menarche was associated with increased birth weight and proportionate birth weight. Our data suggest that the moderating influence of the childhood psychosocial environment on the association between age at menarche and parental investment throughout gestation operates in a dose-dependent manner.
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Affiliation(s)
- David A Coall
- Department of Psychology, University of Basel, Switzerland.
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Whitten PL, Turner TR. Endocrine mechanisms of primate life history trade-offs: Growth and reproductive maturation in vervet monkeys. Am J Hum Biol 2009; 21:754-61. [DOI: 10.1002/ajhb.20939] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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Kramer KL, Greaves RD, Ellison PT. Early reproductive maturity among Pumé foragers: Implications of a pooled energy model to fast life histories. Am J Hum Biol 2009; 21:430-7. [PMID: 19402033 DOI: 10.1002/ajhb.20930] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Life history theory places central importance on relationships between ontogeny, reproduction, and mortality. Fast human life histories have been theoretically and empirically associated with high mortality regimes. This relationship, however, poses an unanswered question about energy allocation. In epidemiologically stressful environments, a greater proportion of energy is allocated to immune function. If growth and maintenance are competing energetic expenditures, less energy should be available for growth, and the mechanism to sustain rapid maturation remains unclear. The human pattern of extended juvenile provisioning and resource sharing may provide an important source of variation in energy availability not predicted by tradeoff models that assume independence at weaning. We consider a group of South American foragers to evaluate the effects that pooled energy budgets may have on early reproduction. Despite growing up in an environment with distinct seasonal under-nutrition, harsh epidemiological conditions, and no health care, Pumé girls mature quickly and initiate childbearing in their midteens. Pooled energy budgets compensate for the low productivity of girls not only through direct food transfers but importantly by reducing energy they would otherwise expend in foraging activities to meet metabolic requirements. We suggest that pooled energy budgets affect energy availability at both extrinsic and intrinsic levels. Because energy budgets are pooled, Pumé girls and young women are buffered from environmental downturns and can maximize energy allocated to growth completion and initiate reproduction earlier than a traditional bound-energy model would predict.
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Affiliation(s)
- Karen L Kramer
- Department of Anthropology, Harvard University, Cambridge, Massachusetts 02138, USA.
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