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Menarcheal timing is associated with growth, development, health, wellbeing, and reproduction across the lifespan. Although sexual orientation is a known correlate of health and developmental inequities, relatively little evolutionarily framed research has investigated sexual orientation-based variation in maturational timing. To improve our understanding of menarcheal timing among sexual minority (SM) people, we use a biocultural-evolutionary life history lens that takes into account the stresses of minoritization to examine the relationship between sexual orientation and self-reported age at menarche in a sample of American adults.Using the U.S. National Health and Nutrition Examination Survey (NHANES), a large, nationally representative dataset (n = 9757), we fit multiple logistic regression models and survival curves to evaluate associations between sexual orientation, indicators of somatic and material resources during adolescence (e.g., education, citizenship, upper arm length), and self-reported menarche.SM respondents were more likely to report earlier (by 4-5 months) ages of menarche (p .001). Post-hoc tests revealed that these differences were driven by bisexual (p .001) and same-sex experienced (p .001) relative to heterosexual and lesbian/gay respondents. Earlier menarcheal timing among SM respondents persisted after adjusting for socio-demographic factors and proxies of developmental conditions.Our findings reveal that SM status is associated with earlier ages of menarche, an important social and reproductive milestone. We argue that uniting life history theory with the minority stress hypothesis better explains differences in menarcheal timing by sexual orientation than previous paradigms. Investigators should attend to sexual orientation-based variation in maturational timing using holistic, inclusive approaches.

Globally, mortality and fertility rates generally fall as resource abundance increases. This pattern represents an evolutionary paradox insofar as resource-rich ecological contexts can support higher numbers of offspring, a component of biological fitness. This paradox has not been resolved, in part because the relationships between fertility, life history strategies, reproductive behavior, and socioeconomic conditions are complex and cultural-historically contingent. We aim to understand how we might make sense of this paradox in the specific context of late-twentieth-century, mid–demographic transition Chile. We use distribution-specific generalized linear models to analyze associations between fertility-related life-history traits—number of offspring, ages at first and last reproduction, average interbirth interval, and average number of live births per reproductive span year—and socioeconomic position (SEP) using data from a cohort of 6,802 Chilean women born between 1961 and 1970. We show that Chilean women of higher SEP have shorter average interbirth intervals, more births per reproductive span year, later age at first reproduction, earlier ages at last reproduction, and, ultimately, fewer children than women of lower SEP. Chilean women of higher SEP consolidate childbearing over a relatively short time span in the middle of their reproductive careers, whereas women of lower SEP tend to reproduce over the entirety of their reproductive lifespans. These patterns may indicate that different SEP groups follow different pathways toward declining fertility during the demographic transition, reflecting different life-history trade-offs in the process.

ObjectiveAcademic human biology seeks to characterize and explain human biocultural variation in terms of adaptations to local environments. Understanding and educating about such variation, if not carried out thoughtfully, can reinforce power asymmetries around who can produce and access the knowledge, and in what ways and places. One of many factors contributing to power inequities in knowledge production and access concerns histories of state-driven colonization, with people(s) dispossessed of land through colonization generally having relatively less power.Because human biologists disproportionately work with communities/sub-populations living in marginal environments, most of which have been moved, dispossessed, and/or reconfigured through colonization, we are prone to reproducing these land-related power imbalances but we are also well-situated to level them.MethodsHere, we do three things we hope will move us toward research and teaching practices that recognize and begin to disrupt colonial power inequities in human biology knowledge production and access.ResultsFirst, after defining terms core to understanding the power matrices at stake, we outline likely benefits to human biologists of using anticolonial approaches. Second, we highlight two frameworks offering anticolonial tools (community-based participatory research and “two-eyed seeing”). Third, we suggest several practical, behavioral changes to make and skills to develop for human biologists looking to shift power balances.ConclusionWe conclude by reflecting on our own positions along the colonially rooted power gradients structuring human biology. We argue that doing so constitutes an essential early step toward creating anticolonial spaces for more ethical and just production, consumption, and application of knowledge.

Across populations, human morbidity and mortality risks generally follow clear gradients, with socially-disadvantaged individuals and groups tending to have higher morbidity and mortality at all life stages relative to those more socially advantaged. Anthropologists specialize in understanding the proximate and ultimate factors that shape variation in human biological functioning and health and are therefore well-situated to explore the relationships between social position and health in diverse ecological and cultural contexts. While human biologists have developed sophisticated methods for assessing health using minimally-invasive methods, at a disciplinary level, we have room for conceptual and methodological improvement in how we frame, measure, and analyze the social inequities that might shape health inequities. This toolkit paper elaborates on some necessary steps for human biologists to further enhance the quality of our research on health inequities. Specifically, we address: (1) how to frame unequal health outcomes (i.e., inequalities vs. disparities vs. inequities) and the importance of identifying our conceptual models of how these inequities emerge; (2) how to measure various axes of social inequities across diverse cultural contexts, and (3) approaches to community collaboration and dissemination. We end by discussing (4) future directions in human biology research of health inequities, including understanding the ultimate causes of sensitivity to social inequities and transitioning from research to action.

Objectives Gestational weight gain (GWG) is increasingly monitored in the United States and Canada. While promoting healthy GWG offers benefits, there may be costs with over-surveillance. We aimed to explore these costs/benefits. Methods Quantitative data from 350 pregnant survey respondents and qualitative focus group data from 43 pregnant/post-partum and care-provider participants were collected in the Mothers to Babies (M2B) study in Hamilton, Canada. We report descriptive statistics and discussion themes on GWG trajectories, advice, knowledge, perceptions, and pregnancy diet. Relationships between GWG monitoring/normalization and worry, knowledge, diet quality, and sociodemographics-namely low-income and racialization-were assessed using χ2 tests and a linear regression model and contextualized with focus group data. Results Most survey respondents reported GWG outside recommended ranges but rejected the mid-20th century cultural norm of "eating for two"; many worried about gaining excessively. Conversely, respondents living in very low-income households were more likely to be gaining less than recommended GWG and to worry about gaining too little. A majority had received advice about GWG, yet half were unable to identify the range recommended for their prepregnancy BMI. This proportion was even lower for racialized respondents. Pregnancy diet quality was associated with household income, but not with receipt or understanding of GWG guidance. Care-providers encouraged normalized GWG, while worrying about the consequences of pathologizing "abnormal" GWG. Conclusions Translation of GWG recommendations should be done with a critical understanding of GWG biological normalcy. Supportive GWG monitoring and counseling should consider clinical, socioeconomic, and community contexts.

Objective:To disrupt cycles of health inequity, traceable to dietary inequities in the earliest stages of life, public health interventions should target improving nutritional wellbeing in preconception/pregnancy environments. This requires a deep engagement with pregnant/postpartum people (PPP) and their communities (including their health and social care providers, HSCP). We sought to understand the factors that influence diet during pregnancy from the perspectives of PPP and HSCP, and to outline intervention priorities.Design:We carried out thematic network analyses of transcripts from ten focus group discussions (FGD) and one stakeholder engagement meeting with PPP and HSCP in a Canadian city. Identified themes were developed into conceptual maps, highlighting local priorities for pregnancy nutrition and intervention development.Setting:FGD and the stakeholder meeting were run in predominantly lower socioeconomic position (SEP) neighbourhoods in the sociodemographically diverse city of Hamilton, Canada.Participants:All local, comprising twenty-two lower SEP PPP and forty-three HSCP.Results:Salient themes were resilience, resources, relationships and the embodied experience of pregnancy. Both PPP and HSCP underscored that socioeconomic-political forces operating at multiple levels largely determined the availability of individual and relational resources constraining diet during pregnancy. Intervention proposals focused on cultivating individual and community resilience to improve early-life nutritional environments. Participants called for better-integrated services, greater income supports and strengthened support programmes.Conclusions:Hamilton stakeholders foregrounded social determinants of inequity as main factors influencing pregnancy diet. They further indicated a need to develop interventions that build resilience and redistribute resources at multiple levels, from the household to the state.

Variation in the durations of exclusive breastfeeding (exBF) and any breastfeeding (anyBF) is associated with socioecological factors. This plasticity in breastfeeding behavior appears adaptive, but the mechanisms involved are unclear. With this concept in mind, we investigated whether durations of exBF and anyBF in a rural Maya population covary with markers of a form of socioecological change—market integration—and whether individual factors (individual learning, physiological plasticity) and/or learning from others in the community (social learning, norm adherence) mediate these changes. Using data from 419 mother-child pairs from two Guatemalan Maya villages, we fit a bivariate linear mixed model. The model compared exBF and anyBF among children from households of varying degrees of market integration whose mothers follow what we inferred to be local infant-feeding norms. It controlled for other factors expected to affect breastfeeding durations. We found evidence that exBF is associated with whether mothers follow their population’s infant feeding norms, but no evidence that exBF is associated with the household’s level of market integration. Conversely, anyBF is significantly associated with the household’s market integration, but not with the villages’ inferred norms. Because deviations from exBF norms are likely to result in infant mortality and reduced fitness, we hypothesize that the incentive to conform is relatively strong. Relatively greater individual plasticity in anyBF allows mother-child pairs to tailor it to socioecological conditions. Deviations from anyBF norms may be tolerated because they may provide later-life health/fitness payoffs, while posing few risks to infant survival.

Environmental factors affecting development through embryogenesis, pregnancy, and infancy impact health through all subsequent stages of life. Known as the Developmental Origins of Health and Disease (DOHaD) hypothesis, this concept is widely accepted among health and social scientists. However, it is unclear whether DOHaD-based ideas are reaching the general public and/or influencing behaviour. This study thus investigated whether and under what circumstances pregnant people in Canada are familiar with DOHaD, and if DOHaD familiarity relates to eating behaviour. Survey responses from pregnant people from Hamilton, Canada, were used to assess respondents' knowledge of DOHaD (hereafter, DOHaDKNOWLEDGE) compared with their knowledge of more general pregnancy health recommendations (Pregnancy GuidelineKNOWLEDGE). The survey also characterized respondents' pregnancy diet quality and sociodemographic profiles. We fit two multiple, linear, mixed regression models to the data, one with DOHaDKNOWLEDGE score as the dependent variable and the other with diet quality score as the dependent. In both models, responses were clustered by respondents' neighbourhoods. Complete, internally consistent responses were available for 330 study-eligible respondents. Relative to Pregnancy GuidelineKNOWLEDGE, respondents had lower, more variable DOHaDKNOWLEDGE scores. Additionally, higher DOHaDKNOWLEDGE was associated with higher socio-economic position, older age, and lower parity, independent of Pregnancy GuidelineKNOWLEDGE. Diet quality during pregnancy was positively associated with DOHaDKNOWLEDGE, adjusting for sociodemographic factors. A subset of relatively high socio-economic position respondents was familiar with DOHaD. Greater familiarity with DOHaD was associated with better pregnancy diet quality, hinting that translating DOHaD knowledge to pregnant people may motivate improved pregnancy nutrition and thus later-life health for developing babies.

Evidence supporting the Developmental Origins of Health and Disease (DOHaD) hypothesis indicates that improving early life environments can reduce non-communicable disease risks and improve health over the lifecourse. A widespread understanding of this evidence may help to reshape structures, guidelines and individual behaviors to better the developmental conditions for the next generations. Yet, few efforts have yet been made to translate the DOHaD concept beyond the research community. To understand why, and to identify priorities for DOHaD Knowledge Translation (KT) programs, we review here a portion of published descriptions of DOHaD KT efforts and critiques thereof. We focus on KT targeting people equipped to apply DOHaD knowledge to their everyday home or work lives. We identified 17 reports of direct-to-public DOHaD KT that met our inclusion criteria. Relevant KT programs have been or are being initiated in nine countries, most focusing on secondary school students or care-workers-in-training; few target parents-to-be. Early indicators suggest that such programs can empower participants. Main critiques of DOHaD KT suggest it may overburden mothers with responsibility for children’s health and health environments, minimizing the roles of other people and institutions. Simultaneously, though, many mothers-to-be seek reliable guidance on prenatal health and nutrition, and would likely benefit from engagement with DOHaD KT. We thus recommend emphasizing solidarity, and bringing together people likely to one day become parents (youth), people planning pregnancies, expecting couples, care workers and policymakers into empowering conversation about DOHaD and about the importance and complexity of early life environments.

Biocultural theory is an integrative research program designed to investigate the causal interactions between biological adaptations and cultural constructions. From the biocultural perspective, cultural processes are rooted in the biological necessities of the human life cycle: specifically human forms of birth, growth, survival, mating, parenting, and sociality. Conversely, from the biocultural perspective, human biological processes are constrained, organized, and developed by culture, which includes technology, culturally specific socioeconomic and political structures, religious and ideological beliefs, and artistic practices such as music, dance, painting, and storytelling. Establishing biocultural theory as a program that self-consciously encompasses the different particular forms of human evolutionary research could help scholars and scientists envision their own specialized areas of research as contributions to a coherent, collective research program. This article argues that a mature biocultural paradigm needs to be informed by at least 7 major research clusters: (a) gene-culture coevolution; (b) human life history theory; (c) evolutionary social psychology; (d) anthropological research on contemporary hunter-gatherers; (e) biocultural socioeconomic and political history; (f) evolutionary aesthetics; and (g) biocultural research in the humanities (religions, ideologies, the history of ideas, and the arts). This article explains the way these research clusters are integrated in biocultural theory, evaluates the level of development in each cluster, and locates current biocultural theory within the historical trajectory of the social sciences and the humanities. Biocultural theory is an integrative research program designed to investigate the causal interactions between biological adaptations and cultural constructions. From the biocultural perspective, cultural processes are rooted in the biological necessities of the human life cycle: specifically human forms of birth, growth, survival, mating, parenting, and sociality. Conversely, from the biocultural perspective, human biological processes are constrained, organized, and developed by culture, which includes technology, culturally specific socioeconomic and political structures, religious and ideological beliefs, and artistic practices such as music, dance, painting, and storytelling. Establishing biocultural theory as a program that self-consciously encompasses the different particular forms of human evolutionary research could help scholars and scientists envision their own specialized areas of research as contributions to a coherent, collective research program. This article argues that a mature biocultural paradigm needs to be informed by at least 7 major research clusters: (a) gene-culture coevolution; (b) human life history theory; (c) evolutionary social psychology; (d) anthropological research on contemporary hunter-gatherers; (e) biocultural socioeconomic and political history; (f) evolutionary aesthetics; and (g) biocultural research in the humanities (religions, ideologies, the history of ideas, and the arts). This article explains the way these research clusters are integrated in biocultural theory, evaluates the level of development in each cluster, and locates current biocultural theory within the historical trajectory of the social sciences and the humanities.

Objectives The causes of variation in breastfeeding duration in humans are poorly understood, but life history factors related to maternal energetics drive much of the variation in lactation duration in nonhuman animals. With this in mind, we investigated whether four energy-related factors influence variation in breastfeeding duration in a non-industrial human population: (1) mortality risk during mother's development (assessed via mother's adult height), (2) reliance on nutrient-dense weaning foods, (3) access to and need for help with infant feeding and care (“allomaternal care”), and (4) maternal tradeoffs between current and future reproduction (measured via child's birth order). Materials and methods The data pertain to 51 Kakchiquel-speaking Maya mothers and 283 children from a village in rural Guatemala. We developed a linear mixed model to evaluate the relationships between breastfeeding duration and the energy-related factors. Results Duration of breastfeeding was associated with two of the energy-related factors in the ways we predicted but not with the other two. Contrary to predictions, taller mothers breastfed for shorter periods and we found no evidence that weanling diet quality impacts breastfeeding duration. As predicted, women who had more help with infants breastfed for shorter periods, and later-born infants breastfed longer than earlier-born ones. Discussion The results regarding allomaternal care suggest that help reduces mothers' lactation demands. The energy saved may be redirected to increasing fecundity or investment in other children. The birth order result suggests that children born to mothers nearing reproductive senescence receive higher levels of investment, which likely impacts children's fitness.

Women often experience novel food aversions and cravings during pregnancy. These appetite changes have been hypothesized to work alongside cultural strategies as adaptive responses to the challenges posed by pregnancy (e.g., maternal immune suppression). Here, we report a study that assessed whether data from an indigenous population in Fiji are consistent with the predictions of this hypothesis. We found that aversions focus predominantly on foods expected to exacerbate the challenges of pregnancy. Cravings focus on foods that provide calories and micronutrients while posing few threats to mothers and fetuses. We also found that women who experience aversions to specific foods are more likely to crave foods that meet nutritional needs similar to those provided by the aversive foods. These findings are in line with the predictions of the hypothesis. This adds further weight to the argument that appetite changes may function in parallel with cultural mechanisms to solve pregnancy challenges.

We report a study on nausea and vomiting of pregnancy (NVP) and pregnancy-related food aversions in a small-scale society from Yasawa Island, Fiji. Because NVP has rarely been studied quantitatively in small-scale populations, we begin with a detailed description of its expression among the women of Yasawa. We found that 66% of these women experience nausea and/or vomiting in tandem with the development of aversions to certain foods. This pattern of expression is similar to what has been documented for industrialized populations, and the prevalence of 66% is close to the industrialized mean prevalence of 69%. We then use the data from the women of Yasawa to evaluate the three main hypotheses that have been put forward to explain the evolution and ecological function of NVP. We show that food aversions of pregnancy focus preferentially on food types that are more likely to carry pathogens or contain chemical toxins. Such aversions do not focus on nutrient-dense foods or on frequently encountered foods. These findings are most consistent with the hypothesis that NVP, along with pregnancy-related aversions, evolved to motivate women to avoid exposure to diseases and other toxins when they are immune-compromised by pregnancy and during a critical period of embryo development. These findings contribute to a growing body of theoretical and empirical literature that suggests that NVP symptoms represent a series of adaptations rather than pathological responses to the physiological demands of pregnancy.

When dealing with the northern boundary of Neanderthals ( Homo neanderthalensis ) and the question of whether or not they dispersed into Southern Scandinavia, two contradictory hypotheses can be identified. The first, and also the most widely endorsed, hereafter, hypothesis A, argues primarily that Neanderthals did not occupy regions above 55°N because of 1) climatic constraints and 2) dispersal barriers. The second, hypothesis B, argues that they possibly occasionally dispersed above 55°N, but that factors such as 1) research- and/or 2) taphonomic bias are responsible for their archaeological invisibility. Here, we report an evaluation of these competing hypotheses. To this end, we reconstruct the environment for the time period and region of interest (the Last Interglacial Complex and Northern Germany and Southern Scandinavia), based on three lines of evidence: palaeoenvironmental reconstruction combined with a novel habitat modelling approach, a review of relevant archaeological localities, and a discussion of the possible impacts of both research biases and the taphonomic effects on the archaeological data. We focus particularly on the climatic and geological explanatory factors relevant to the two hypotheses. Our results are inconsistent with the claim that climatic constraint and/or a lack of suitable habitats can fully explain the absence of Neanderthals in Southern Scandinavia during the Eemian Interglacial and Early Weichselian Glaciation. We do, however, find evidence that a geographic barrier may have impeded northerly migrations during the Eemian. The evidence reviewed here suggests that both research bias and taphonomy – consistent with hypothesis B – could account for the archaeological invisibility of Neanderthals in Southern Scandinavia, highlighting the need for further strategic survey and/or excavation efforts in the region.

Globally, mothers from a wide variety of socio-environmental contexts often assume slow-growing babies are underfed and erroneously attribute perceived growth retardation to inadequate milk supply or poor milk quality [1]. These assumptions frequently prompt replacement of breastmilk with formula or other nonbreastmilk foods to encourage infant weight and length gains [1]. This tendency to truncate breastfeeding to accelerate growth is exacerbated by some features of contemporary environments in both developing and developed nations such as growing rates of maternal obesity and caesarean section that interfere with breastfeeding. Unfortunately, regardless of the primary reason for truncation, cessation of exclusive breastfeeding before 4–6 months and of continued breastfeeding before 12 months is associated with increased risk of gastrointestinal infections and poor immune system development in infancy, and obesity and a variety of non-communicable diseases in later life [2]. Although stunting and wasting in children do represent major public health challenges in lowand middle-income countries, these phenomena should not be confused with unfaltering growth less than two standard deviations below global averages. EVOLUTIONARY PERSPECTIVES