David Lawson | University of California, Santa Barbara (original) (raw)
Papers by David Lawson
Nature Human Behavior, 2021
Nature Human Behaviour, 2019
Approximately 40% of women in sub-Saharan Africa marry before their eighteenth birthday1. Within ... more Approximately 40% of women in sub-Saharan Africa marry before their eighteenth birthday1. Within the international development sector, this phenomenon is referred to as ‘child marriage’, widely equated to forced marriage, and recognized as damaging to multiple dimensions of female well-being1,2. An escalating global campaign to end early marriage typically assumes that its high prevalence is driven by a conflict of inter- ests between parents and daughters, with parents coercing daughters to marry early for the parents’ economic benefit3. However, a parent–offspring conflict model of early marriage has not been explicitly tested. Here we present a study of mar- riage transitions in rural Tanzania, where marriage before or just after 18 years of age is normative. Consistent with paren- tal coercion, we find that bridewealth transfers are highest for younger brides. However, autonomy in partner choice is very common at all ages, relationships between age at mar- riage and female well-being are largely equivocal, and women who marry early achieve relatively higher reproductive suc- cess. We conclude that, in contexts in which adolescents have autonomy in marriage choices and in which marriage pro- motes economic and social security, early marriage may be better understood as serving the strategic interests of both parents and daughters.
Variation in male testosterone has been hypothesized to reflect the evolved hormonal regulation o... more Variation in male testosterone has been hypothesized to reflect the evolved hormonal regulation of investment in mating versus parenting effort. Supporting this hypothesis, numerous studies have observed lower testosterone in married men and fathers compared with unpartnered and childless men, consistent with relatively elevated resource allocation to parenting as opposed to mating effort. Furthermore, lower testosterone has been reported among fathers more actively engaged in direct caregiv-ing. However, it remains unclear whether these findings generalize cross-culturally. Most studies have been conducted in relatively urban, affluent, and low fertility settings where marriage is predominantly monogamous. We contribute new data on testosterone variation in 100 rural Gambian men from a polygynous, high fertility population, where cultural norms dictate that marriage and fatherhood occur in close succession. Married men (almost exclusively fathers) had lower average morning salivary testosterone than unmarried men (almost exclusively childless). This difference, however, could not be statistically differentiated from declines in testosterone observed with age. Independently of age differences and other potential confounds, we find that (i) among married men, polygynously married men had higher afternoon testosterone than monogamously married men; and (ii) fathers who sleep in the same room as their children had lower Adaptive Human Behavior and Physiology
Evolutionary Anthropology Issues News and Reviews
Evolutionary anthropology provides a powerful theoretical framework for understanding how both cu... more Evolutionary anthropology provides a powerful theoretical framework for understanding how both current environments and legacies of past selection shape human behavioral diversity. This integrative and pluralistic field, combining ethnographic, demographic, and sociological methods, has provided new insights into the ultimate forces and proximate pathways that guide human adaptation and variation. Here, we present the argument that evolutionary anthropological studies of human behavior also hold great, largely untapped, potential to guide the design, implementation, and evaluation of social and public health policy. Focusing on the key anthropological themes of reproduction, production, and distribution we highlight classic and recent research demonstrating the value of an evolutionary perspective to improving human well-being. The challenge now comes in transforming relevance into action and, for that, evolutionary behavioral anthropologists will need to forge deeper connections wi...
Proceedings of the Royal Society B-Biological Sciences, 2014
The idea that symmetry in facial traits is associated with attractiveness because it reliably ind... more The idea that symmetry in facial traits is associated with attractiveness because it reliably indicates good physiological health, particularly to potential sexual partners, has generated an extensive literature on the evolution of human mate choice. However, large-scale tests of this hypothesis using direct or longitudinal assessments of physiological health are lacking. Here, we investigate relationships between facial fluctuating asymmetry (FA) and detailed individual health histories in a sample (n ¼ 4732) derived from a large longitudinal study (Avon Longitudinal Study of Parents and Children) in South West England. Facial FA was assessed using geometric morphometric analysis of facial landmark configurations derived from three-dimensional facial scans taken at 15 years of age. Facial FA was not associated with longitudinal measures of childhood health. However, there was a very small negative association between facial FA and IQ that remained significant after correcting for a positive allometric relationship between FA and face size. Overall, this study does not support the idea that facial symmetry acts as a reliable cue to physiological health. Consequently, if preferences for facial symmetry do represent an evolved adaptation, then they probably function not to provide marginal fitness benefits by choosing between relatively healthy individuals on the basis of small differences in FA, but rather evolved to motivate avoidance of markers of substantial developmental disturbance and significant pathology.
PloS one, 2014
The Maasai of northern Tanzania, a semi-nomadic ethnic group predominantly reliant on pastoralism... more The Maasai of northern Tanzania, a semi-nomadic ethnic group predominantly reliant on pastoralism, face a number of challenges anticipated to have negative impacts on child health, including marginalisation, vulnerabilities to drought, substandard service provision and on-going land grabbing conflicts. Yet, stemming from a lack of appropriate national survey data, no large-scale comparative study of Maasai child health has been conducted. Savannas Forever Tanzania surveyed the health of over 3500 children from 56 villages in northern Tanzania between 2009 and 2011. The major ethnic groups sampled were the Maasai, Sukuma, Rangi, and the Meru. Using multilevel regression we compare each ethnic group on the basis of (i) measurements of child health, including anthropometric indicators of nutritional status and self-reported incidence of disease; and (ii) important proximate determinants of child health, including food insecurity, diet, breastfeeding behaviour and vaccination coverage. ...
Philosophical Transactions of the Royal Society B: Biological Sciences, 2011
Journal of Evolutionary Psychology, 2007
Behavioral Ecology, 2013
We would like to thank our 4 sets of commentators for their stimulating and supportive words. The... more We would like to thank our 4 sets of commentators for their stimulating and supportive words. Their reactions give us some hope that our characterization of the field was not wildly off the mark and confirm our belief that the issues we identified in our paper as open questions really are open questions. We agree with many of the points raised and will not repeat them one by one here. A major theme that arises from all of them is that behavioral ecology (BE), perhaps of humans in particular, cannot afford to ignore the mechanisms by which behaviors are acquired. We would like to make 3 points about this position.
In this chapter, we consider what evolutionary anthropology contributes to the study of populatio... more In this chapter, we consider what evolutionary anthropology contributes to the study of population health, focusing specifically on family structure and its relationship to child and adult physical health. Evolutionary anthropologists have now built a substantial body of literature on relationships between family structure and various dimensions of human wellbeing, particularly in the context of small-scale 'traditional' societies and developing rural communities most at risk of poor health outcomes. Crucially, they have also constructed theoretical models to account for variation in key dimensions of family structure in relation to individual, ecological and cultural factors. Thus evolutionary anthropologists have much to say, not only about the extent to which specific family structures may influence health, but also why certain family forms may persist or change across time and space. Here, focusing on studies primarily conducted in sub-Saharan Africa, we review the literature on three interrelated dimensions of family structure and their relationship to health (i) family size, (ii) polygynous vs. monogamous marriage, and (iii) the role of extended kin. Using these examples, we highlight the theoretical and empirical contributions of evolutionary anthropology and draw out implications for population policy and related initiatives seeking to improve family health in the developing world. Evolutionary anthropology has much to offer population health science, both as a rich and integrative theoretical framework and as an active producer of a now substantial body of relevant empirical literature. Here we focus specifically on the study of family structure and its relationship to child and adult physical health in the developing world. Family and health are intimately tied. Family formation defines residence and relatedness, and so fundamentally determines patterns of resource production, allocation and consumption. The family is also a key site for navigating conflicts of interest between individuals: including conflicts between consumers over limited resources, but also conflict between generations, between the sexes, and with and between extended kin, which often have different priorities to individuals within the nuclear family. All of these factors mean that family structure is anticipated to influence health. Health is also one of the many factors that determine the assortment of individuals into particular family structure types. Research on family structure as a determinant of child and adult health must therefore always be cognizant of misinterpreting correlation as causality. Healthier individuals, for example, find it easier to reproduce successfully, are more likely to survive to old age, are more attractive as marriage partners, and are more able to assert their own autonomy or dominance when conflicts of interest arise. This bi-directional relationship between family structure and health represents an important research theme we return to throughout the chapter.
In this chapter, we consider what evolutionary anthropology contributes to the study of populatio... more In this chapter, we consider what evolutionary anthropology contributes to the study of population health, focusing specifically on family structure and its relationship to child and adult physical health. Evolutionary anthropologists have now built a substantial body of literature on relationships between family structure and various dimensions of human wellbeing, particularly in the context of smallscale 'traditional' societies and developing rural communities most at risk of poor health outcomes. Crucially, they have also constructed theoretical models to account for variation in key dimensions of family structure in relation to individual, ecological, and cultural factors. Thus, evolutionary anthropologists have much to say, not only about the extent to which specific family structures may influence health but also why certain family forms may persist or change across time and space. Here, focusing on studies primarily conducted in sub-Saharan Africa, we review the literature on three interrelated dimensions of family structure and their relationship to health: (1) family size, (2) polygynous versus monogamous marriage, and (3) the role of extended kin. Using these examples, we highlight the theoretical and empirical contributions of evolutionary anthropology and draw out implications for population policy and related initiatives seeking to improve family health in the developing world.
Growing up with many siblings, at least in the context of modern post-industrial low fertility, l... more Growing up with many siblings, at least in the context of modern post-industrial low fertility, low mortality societies, is predictive of relatively poor performance on school tests in childhood, lower levels of educational attainment, and lower income throughout adulthood. Recent studies further indicate these relationships hold across generations, so that the descendants of those who grow up with many siblings are also at an apparent socioeconomic disadvantage. In this paper we add to this literature by considering whether such relationships interact with the sex and relative age of siblings. To do this we utilise a unique Swedish multigenerational birth cohort study that provides sibling configuration data on over 10,000 individuals born in 1915-1929, plus all their direct genetic descendants to the present day. Adjusting for parental and birth characteristics, we find that the 'socioeconomic cost' of growing up in a large family is independent of both the sex of siblings and the sex of the individual. However, growing up with several older as opposed to several younger siblings is predictive of relatively poor performance on school tests and a lower likelihood of progression to tertiary education. This later-born disadvantage also holds across generations, with the children of those with many older siblings achieving lower levels of educational attainment. Despite these differences, we find that while individual and descendant income is negatively related to the number of siblings, it is not influenced by the relative age of siblings. Thus, our findings imply that the educational disadvantage of later-born children, demonstrated here and in numerous other studies, does not necessarily translate into reduced earnings in adulthood. We discuss potential explanations for this pattern of results, and consider some important directions for future research into sibling configuration and wellbeing in modern societies.
Human behavioral ecology (HBE) is the study of human behavior from an adaptive perspective. It fo... more Human behavioral ecology (HBE) is the study of human behavior from an adaptive perspective. It focuses in particular on how human behavior varies with ecological context. Although HBE is a thriving research area, there has not been a major review published in a journal for over a decade, and much has changed in that time. Here, we describe the main features of HBE as a paradigm, and review HBE research published since the millennium. We find that the volume of HBE research is growing rapidly, and its composition is changing in terms of topics, study populations, methodology, and disciplinary affiliations of authors. We identify the major strengths of HBE research as its vitality, clear predictions, empirical fruitfulness, broad scope, conceptual coherence, ecological validity, increasing methodological rigor and topical innovation. Its weaknesses include a relative isolation from the rest of behavioral ecology and evolutionary biology, and a somewhat limited current topic base. As HBE continues to grow, there is a major opportunity for it to serve as a bridge between the natural and social sciences, and help unify disparate disciplinary approaches to human behavior. HBE also faces a number of open questions, such as how understanding of proximate mechanisms is to be integrated with behavioral ecology's traditional focus on optimal behavioral strategies, and the causes and extent of maladaptive behavior in humans.
Nature Human Behavior, 2021
Nature Human Behaviour, 2019
Approximately 40% of women in sub-Saharan Africa marry before their eighteenth birthday1. Within ... more Approximately 40% of women in sub-Saharan Africa marry before their eighteenth birthday1. Within the international development sector, this phenomenon is referred to as ‘child marriage’, widely equated to forced marriage, and recognized as damaging to multiple dimensions of female well-being1,2. An escalating global campaign to end early marriage typically assumes that its high prevalence is driven by a conflict of inter- ests between parents and daughters, with parents coercing daughters to marry early for the parents’ economic benefit3. However, a parent–offspring conflict model of early marriage has not been explicitly tested. Here we present a study of mar- riage transitions in rural Tanzania, where marriage before or just after 18 years of age is normative. Consistent with paren- tal coercion, we find that bridewealth transfers are highest for younger brides. However, autonomy in partner choice is very common at all ages, relationships between age at mar- riage and female well-being are largely equivocal, and women who marry early achieve relatively higher reproductive suc- cess. We conclude that, in contexts in which adolescents have autonomy in marriage choices and in which marriage pro- motes economic and social security, early marriage may be better understood as serving the strategic interests of both parents and daughters.
Variation in male testosterone has been hypothesized to reflect the evolved hormonal regulation o... more Variation in male testosterone has been hypothesized to reflect the evolved hormonal regulation of investment in mating versus parenting effort. Supporting this hypothesis, numerous studies have observed lower testosterone in married men and fathers compared with unpartnered and childless men, consistent with relatively elevated resource allocation to parenting as opposed to mating effort. Furthermore, lower testosterone has been reported among fathers more actively engaged in direct caregiv-ing. However, it remains unclear whether these findings generalize cross-culturally. Most studies have been conducted in relatively urban, affluent, and low fertility settings where marriage is predominantly monogamous. We contribute new data on testosterone variation in 100 rural Gambian men from a polygynous, high fertility population, where cultural norms dictate that marriage and fatherhood occur in close succession. Married men (almost exclusively fathers) had lower average morning salivary testosterone than unmarried men (almost exclusively childless). This difference, however, could not be statistically differentiated from declines in testosterone observed with age. Independently of age differences and other potential confounds, we find that (i) among married men, polygynously married men had higher afternoon testosterone than monogamously married men; and (ii) fathers who sleep in the same room as their children had lower Adaptive Human Behavior and Physiology
Evolutionary Anthropology Issues News and Reviews
Evolutionary anthropology provides a powerful theoretical framework for understanding how both cu... more Evolutionary anthropology provides a powerful theoretical framework for understanding how both current environments and legacies of past selection shape human behavioral diversity. This integrative and pluralistic field, combining ethnographic, demographic, and sociological methods, has provided new insights into the ultimate forces and proximate pathways that guide human adaptation and variation. Here, we present the argument that evolutionary anthropological studies of human behavior also hold great, largely untapped, potential to guide the design, implementation, and evaluation of social and public health policy. Focusing on the key anthropological themes of reproduction, production, and distribution we highlight classic and recent research demonstrating the value of an evolutionary perspective to improving human well-being. The challenge now comes in transforming relevance into action and, for that, evolutionary behavioral anthropologists will need to forge deeper connections wi...
Proceedings of the Royal Society B-Biological Sciences, 2014
The idea that symmetry in facial traits is associated with attractiveness because it reliably ind... more The idea that symmetry in facial traits is associated with attractiveness because it reliably indicates good physiological health, particularly to potential sexual partners, has generated an extensive literature on the evolution of human mate choice. However, large-scale tests of this hypothesis using direct or longitudinal assessments of physiological health are lacking. Here, we investigate relationships between facial fluctuating asymmetry (FA) and detailed individual health histories in a sample (n ¼ 4732) derived from a large longitudinal study (Avon Longitudinal Study of Parents and Children) in South West England. Facial FA was assessed using geometric morphometric analysis of facial landmark configurations derived from three-dimensional facial scans taken at 15 years of age. Facial FA was not associated with longitudinal measures of childhood health. However, there was a very small negative association between facial FA and IQ that remained significant after correcting for a positive allometric relationship between FA and face size. Overall, this study does not support the idea that facial symmetry acts as a reliable cue to physiological health. Consequently, if preferences for facial symmetry do represent an evolved adaptation, then they probably function not to provide marginal fitness benefits by choosing between relatively healthy individuals on the basis of small differences in FA, but rather evolved to motivate avoidance of markers of substantial developmental disturbance and significant pathology.
PloS one, 2014
The Maasai of northern Tanzania, a semi-nomadic ethnic group predominantly reliant on pastoralism... more The Maasai of northern Tanzania, a semi-nomadic ethnic group predominantly reliant on pastoralism, face a number of challenges anticipated to have negative impacts on child health, including marginalisation, vulnerabilities to drought, substandard service provision and on-going land grabbing conflicts. Yet, stemming from a lack of appropriate national survey data, no large-scale comparative study of Maasai child health has been conducted. Savannas Forever Tanzania surveyed the health of over 3500 children from 56 villages in northern Tanzania between 2009 and 2011. The major ethnic groups sampled were the Maasai, Sukuma, Rangi, and the Meru. Using multilevel regression we compare each ethnic group on the basis of (i) measurements of child health, including anthropometric indicators of nutritional status and self-reported incidence of disease; and (ii) important proximate determinants of child health, including food insecurity, diet, breastfeeding behaviour and vaccination coverage. ...
Philosophical Transactions of the Royal Society B: Biological Sciences, 2011
Journal of Evolutionary Psychology, 2007
Behavioral Ecology, 2013
We would like to thank our 4 sets of commentators for their stimulating and supportive words. The... more We would like to thank our 4 sets of commentators for their stimulating and supportive words. Their reactions give us some hope that our characterization of the field was not wildly off the mark and confirm our belief that the issues we identified in our paper as open questions really are open questions. We agree with many of the points raised and will not repeat them one by one here. A major theme that arises from all of them is that behavioral ecology (BE), perhaps of humans in particular, cannot afford to ignore the mechanisms by which behaviors are acquired. We would like to make 3 points about this position.
In this chapter, we consider what evolutionary anthropology contributes to the study of populatio... more In this chapter, we consider what evolutionary anthropology contributes to the study of population health, focusing specifically on family structure and its relationship to child and adult physical health. Evolutionary anthropologists have now built a substantial body of literature on relationships between family structure and various dimensions of human wellbeing, particularly in the context of small-scale 'traditional' societies and developing rural communities most at risk of poor health outcomes. Crucially, they have also constructed theoretical models to account for variation in key dimensions of family structure in relation to individual, ecological and cultural factors. Thus evolutionary anthropologists have much to say, not only about the extent to which specific family structures may influence health, but also why certain family forms may persist or change across time and space. Here, focusing on studies primarily conducted in sub-Saharan Africa, we review the literature on three interrelated dimensions of family structure and their relationship to health (i) family size, (ii) polygynous vs. monogamous marriage, and (iii) the role of extended kin. Using these examples, we highlight the theoretical and empirical contributions of evolutionary anthropology and draw out implications for population policy and related initiatives seeking to improve family health in the developing world. Evolutionary anthropology has much to offer population health science, both as a rich and integrative theoretical framework and as an active producer of a now substantial body of relevant empirical literature. Here we focus specifically on the study of family structure and its relationship to child and adult physical health in the developing world. Family and health are intimately tied. Family formation defines residence and relatedness, and so fundamentally determines patterns of resource production, allocation and consumption. The family is also a key site for navigating conflicts of interest between individuals: including conflicts between consumers over limited resources, but also conflict between generations, between the sexes, and with and between extended kin, which often have different priorities to individuals within the nuclear family. All of these factors mean that family structure is anticipated to influence health. Health is also one of the many factors that determine the assortment of individuals into particular family structure types. Research on family structure as a determinant of child and adult health must therefore always be cognizant of misinterpreting correlation as causality. Healthier individuals, for example, find it easier to reproduce successfully, are more likely to survive to old age, are more attractive as marriage partners, and are more able to assert their own autonomy or dominance when conflicts of interest arise. This bi-directional relationship between family structure and health represents an important research theme we return to throughout the chapter.
In this chapter, we consider what evolutionary anthropology contributes to the study of populatio... more In this chapter, we consider what evolutionary anthropology contributes to the study of population health, focusing specifically on family structure and its relationship to child and adult physical health. Evolutionary anthropologists have now built a substantial body of literature on relationships between family structure and various dimensions of human wellbeing, particularly in the context of smallscale 'traditional' societies and developing rural communities most at risk of poor health outcomes. Crucially, they have also constructed theoretical models to account for variation in key dimensions of family structure in relation to individual, ecological, and cultural factors. Thus, evolutionary anthropologists have much to say, not only about the extent to which specific family structures may influence health but also why certain family forms may persist or change across time and space. Here, focusing on studies primarily conducted in sub-Saharan Africa, we review the literature on three interrelated dimensions of family structure and their relationship to health: (1) family size, (2) polygynous versus monogamous marriage, and (3) the role of extended kin. Using these examples, we highlight the theoretical and empirical contributions of evolutionary anthropology and draw out implications for population policy and related initiatives seeking to improve family health in the developing world.
Growing up with many siblings, at least in the context of modern post-industrial low fertility, l... more Growing up with many siblings, at least in the context of modern post-industrial low fertility, low mortality societies, is predictive of relatively poor performance on school tests in childhood, lower levels of educational attainment, and lower income throughout adulthood. Recent studies further indicate these relationships hold across generations, so that the descendants of those who grow up with many siblings are also at an apparent socioeconomic disadvantage. In this paper we add to this literature by considering whether such relationships interact with the sex and relative age of siblings. To do this we utilise a unique Swedish multigenerational birth cohort study that provides sibling configuration data on over 10,000 individuals born in 1915-1929, plus all their direct genetic descendants to the present day. Adjusting for parental and birth characteristics, we find that the 'socioeconomic cost' of growing up in a large family is independent of both the sex of siblings and the sex of the individual. However, growing up with several older as opposed to several younger siblings is predictive of relatively poor performance on school tests and a lower likelihood of progression to tertiary education. This later-born disadvantage also holds across generations, with the children of those with many older siblings achieving lower levels of educational attainment. Despite these differences, we find that while individual and descendant income is negatively related to the number of siblings, it is not influenced by the relative age of siblings. Thus, our findings imply that the educational disadvantage of later-born children, demonstrated here and in numerous other studies, does not necessarily translate into reduced earnings in adulthood. We discuss potential explanations for this pattern of results, and consider some important directions for future research into sibling configuration and wellbeing in modern societies.
Human behavioral ecology (HBE) is the study of human behavior from an adaptive perspective. It fo... more Human behavioral ecology (HBE) is the study of human behavior from an adaptive perspective. It focuses in particular on how human behavior varies with ecological context. Although HBE is a thriving research area, there has not been a major review published in a journal for over a decade, and much has changed in that time. Here, we describe the main features of HBE as a paradigm, and review HBE research published since the millennium. We find that the volume of HBE research is growing rapidly, and its composition is changing in terms of topics, study populations, methodology, and disciplinary affiliations of authors. We identify the major strengths of HBE research as its vitality, clear predictions, empirical fruitfulness, broad scope, conceptual coherence, ecological validity, increasing methodological rigor and topical innovation. Its weaknesses include a relative isolation from the rest of behavioral ecology and evolutionary biology, and a somewhat limited current topic base. As HBE continues to grow, there is a major opportunity for it to serve as a bridge between the natural and social sciences, and help unify disparate disciplinary approaches to human behavior. HBE also faces a number of open questions, such as how understanding of proximate mechanisms is to be integrated with behavioral ecology's traditional focus on optimal behavioral strategies, and the causes and extent of maladaptive behavior in humans.