Our research uses theory from evolution and ecology to study human behavior, demography, and social systems. We seek to understand how the environment and economic systems impact marriage, reproduction, and social inequality.


Our Team

Mary Shenk

Penn State University
Associate Professor of AnthropologyDemography, and Asian Studies
Faculty Associate: Population Research Institute
Faculty Affiliate: Center for Human Ecology

I am a biocultural anthropologist, human behavioral ecologist, and anthropological demographer with interests in marriage, family, kinship, parental investment, fertility, mortality, and inequality. I have conducted field research on the economics of marriage and parental investment in urban South India, the causes of rapid fertility decline in rural Bangladesh, and the effects of market integration on wealth, social networks, and health in rural Bangladesh.

Current Work

  1. Understanding the foundations of inequality and how these shift with both market integration and adaptation to local environments.
  2. Understanding the evolutionary demography of human fertility, including the psychological mechanisms that underpin human reproduction
  3. The behavioral ecology of human kinship, marriage, and family systems.


  • Anth 408: Anthropological Demography
  • Anth 446: Mating and Marriage
  • Anth 458: Ethnographic Field Methods
  • Anth 509: Proposal Writing
  • Anth 573: Research Practicum in Anthropology

My fieldwork focuses on South Asia, particularly Bangladesh and India, but I am also interested in cross-cultural work. I employ both quantitative and qualitative methods of research, and believe that firsthand fieldwork is essential to a deep understanding of social phenomena as well as to ensure that analyses are appropriately designed and findings are understood in socioecological context.

Lisa S. McAllister, Ph.D.

Postdoctoral Scholar: Department of Anthropology, Pennsylvania State University
Lecturer: University of California, Santa Barbara

I am a broadly trained anthropologist with research and teaching interests that incorporate cultural, ecological, and evolutionary perspectives. My research interests are in human growth and development, reproductive decision making, fertility and health disparities. I have conducted field research in Bolivia exploring how socioeconomic change influences reproductive preferences and outcomes, the effects of adolescent reproduction on maternal and child growth and development, and the effects of mortality exposure on reproductive timing and effort.

Current Work

  1. Understanding the psychological mechanisms that influence human reproductive timing and effort.
  2. Understanding the effects of education on reproductive preferences and outcomes when socioeconomic mobility and women’s reproductive autonomy are limited.
  3. Understanding the effects of teenage pregnancy on the mother’s and first-born child’s cognitive and somatic development, and the effects on subsequent births.

With my post-doctoral advisor Mary Shenk (PSU), I manage a multi-site study investigating the psychological mechanisms underlying human reproductive decision making and the environmental cues these mechanisms are attuned to. There is a longstanding interest among demographers, anthropologists, and others, to explain how various socioecological factors influence reproductive preferences, timing and effort, and to separate correlates from causal factors. Consequently, we are also exploring the viability of using experimental methodology, especially priming, to separate causative relationships from correlative ones. In 2018, we begin our cross-cultural study to explore how cultural and economic differences affect the psychological mechanisms underlying our reproductive decision making.

Since 2005, facilitated by the Tsimane Health and Life History Project, I have worked with a population of South American forager-farmers, the Tsimane of Bolivia. This research has two foci: (1) how changing environments affect women’s and men’s fertility preferences and fertility, and consequently women’s reproductive health and autonomy; and (2) how adolescent mothers’ resource allocation — among the competing demands of growth, reproduction and somatic maintenance — affect their and their children’s health, growth and development.

Adolescent Pregnancy and Maternal and Infant Growth and Development

My first project with the Tsimane investigates the effects of early age at first birth and high fertility on maternal growth, health and cognitive development. Women have finite resources. Adolescence is a period of continued growth, and social and cognitive development. Reproducing during adolescence reduces women’s investment in their own growth and somatic maintenance but not completely, such that during gestation and lactation their first-born child receives fewer resources than the first-born children of women who delay their reproduction.

This work explores growth patterns in Tsimane women through adolescence, testing for trade-offs in energetic investment between growth and pregnancy. My findings, to date, support previous research suggesting that early age at first birth stunts maternal growth. However, my findings further suggest that: (1) women who give birth at age 15 or younger continue their growth post-pregnancy (although they are shorter as adults than average); (2) women on faster growth trajectories, do not cease growth earlier and are often taller than average as adults, if their growth is uninterrupted by pregnancy/motherhood; (3) the first-born sons, but not daughters, of mothers aged 15 and younger suffer long-term growth deficits. My future work in this area will investigate the long-term consequences of adolescent reproduction to the growth and health of first born and later born children; and the relationship between age at first birth and maternal and child cognitive development.

Women’s and Men’s Fertility Preference in a Changing Environment

My second project with the Tsimane explores why fertility among the Tsimane remains high (TFR = 9.1) despite small preferred family sizes (IFS = 4 to 5 children), and access to contraceptives and family planning programs. This high fertility, coupled with increasing infant and child survival rates, indicates that the Tsimane population will double in size within 24 years. As the Tsimane are marginalized, face discrimination and have limited land rights, this population growth and the associated environmental degradation are unsustainable. Furthermore, high fertility is associated with negative maternal and child health outcomes and low female autonomy. It is crucial that we better understand the dissonance between these people’s small desired family sizes and fertility, particularly as existing family planning programs and improved access to contraceptives are not having the expected affects.

My research suggests that excess fertility increases with proximity to market towns that provide resource stability and healthcare. Tsimane women living near these urban centers have better maternal condition and likely greater fecundity, which is not countered by increased use of contraceptives. Furthermore, they have low returns on investments in human capital and low socioeconomic mobility: Tsimane women are stuck in their homelands where adult status and success are measured in terms of reproductive status and family size, and sociopolitical power and economic security hinge on large kin networks. Under these conditions, despite a desire for smaller family sizes, women are trapped in a reproductive role, and motivation to delay or reduce reproduction is low. Consequently, adolescent reproduction is the norm for Tsimane women despite trade-offs between maternal and fetal/infant growth, development, cognition and health. However, the evolutionary, sociopolitical and long-term economic advantages (e.g. higher fertility) of an early reproductive start may outweigh these costs. My future work in this area will continue to unravel the interplay between socioeconomic development and evolved life history strategies at the onset of demographic transition.

I have taught several courses at the University of California, Santa Barbara, and been a guest lecturer at California State University – Channel Islands, and Santa Barbara City College. As I am trained in the biological and cultural sub-disciplines of anthropology, as well as demography, biology, and quantitative methods, I utilize a cross-disciplinary approach when teaching. I instruct my students how to use comparative and integrative methods in their research projects. I also believe students need marketable skills and incorporate training and practice of these into my courses.

Courses Taught

  • Introduction to the Evolution of Human Behavior
  • Introduction to Research Methods and Statistics in Anthropology
  • Human Variation
  • Primate Behavioral Ecology
  • Primate and Human Sexual Behavior


McAllister, L., Pepper, G., Hackman, J., Virgo, S., Sobraske, K., Coall, D. (2016), The evolved psychological mechanisms of fertility motivation: Hunting for causation in a sea of correlation. Philosophical Transactions B. 371 (1692), Article no. 20150151

Coall, D. Tickner, M., McAllister, L., Sheppard, P. (2016) Developmental influences on human fertility decisions: An evolutionary perspective. Philosophical Transactions B. 371 (1692), Article no. 20150146

Veile, A., Martin, M., McAllister, L., Gurven, G. (2014) Modernization is Associated with Intensive Breastfeeding Patterns in the Bolivian Amazon. Social Science & Medicine. 100: 148-158

McAllister, L., Gurven, M., Kaplan, H., Steiglitz, J. (2012) Why do women have more children than they want? Understanding differences in women’s ideal and actual family size in a natural fertility population. American Journal of Human Biology. 24(6):786-799

Gurven, M., Winking, J., Kaplan, H., von Rueden, C., McAllister, L. (2009) A bioeconomic approach to marriage and the sexual division of labor. Human Nature. 20(2):151-183

Other Publications

Sears, R., Pepper, G., McAllister, L. (2016) Demography needs you! Why demography needs psychologists. The Psychologist. 26(1): 26-29

In addition to my teaching experience, I have engaged undergraduates in my research. This has involved training undergraduates in analytical thinking, qualitative and quantitative research methods, statistics, project write up for publication, and presentation at conferences. Several students were also provided opportunities to do fieldwork in Bolivia and Bangladesh.

Undergraduate Projects Mentored


2017|Supervising Caitlin Paulson’s undergraduate honors thesis.

Title: Reassessing the relationship between propensity for risk taking and number of tattoos, and how tattoos are perceived in the 21 st century.

Supervised Ema Angeles’ original research project for the Undergraduate Research and Creative Activities Grant at UCSB.

Title: Why do the Tsimane evoke witchcraft to explain familial deaths?


2016|Supervised Madeleine Zoeller’s original research project.

Title: Does mortality risk influence parents’ investment in their children in Matlab, Bangladesh?

  • Miss Zoeller received a Research Experience for Undergraduates grant from the National Science Foundation ($5000) under PI: Mary Shenk, and spent 10 weeks in Matlab, Bangladesh, working on her project. She is now a graduate student at UCLA and will be continuing her work in Bangladesh in 2018.


2015|Supervised Dylan Tweed’s original research project.

Title: Are Life History Variables Sensitive to Priming? A multi-level meta-analysis of 92 results from 41 studies.

  • Mr. Tweed presented his research as a poster at the annual conference of the Human Behavior and Evolution Society, Columbia, MO. He received a $500 grant from NESCent to attend this conference. He is now a graduate student at Harvard.

Supervised Ivanna Robeldo’s original research project for the Undergraduate Research Colloquium at UCSB.

Title: Factors associated with Tuberculosis risk among Bolivian forager-farmers.

  • Miss Robeldo presented her research as a poster at the annual Undergraduate Research Colloquium at UCSB.


2012|Supervised Geni Garcia’s undergraduate honors thesis.

Title: The effects of Teenage Pregnancy on Maternal and Child Growth among Bolivian forager-farmers.

  • I received the Fiona Goodchild Award for Excellence as a Graduate Mentor of Undergraduate Research .
  • Ms. Garcia presented her research as a poster at the 2014 UC Global Health Day at UC Davis, CA, and at the annual Undergraduate Research Colloquium at UCSB.
  • Ms. Garcia won the 2012 award for Outstanding Research in the Social Sciences at UCSB for this project. Ms. Garcia also spent six months working with the Tsimane of Bolivia post-graduation.

Jane Lankes, M.A.

I am a Ph.D. Candidate in Sociology and Demography with interests in motherhood, marriage, religion, health, and quantitative methods. My dissertation focuses on maternal investment and maternal well-being. Together with Dr. Shenk, I research various topics related to dowry in South Asia.

Intensive Mothering and Maternal Physical Health

Dissertation Chair(s):
Dr. Sarah Damaske

Research Interests:
Family, Gender, Health, Food, Religion, Demography, Quantitative Methods

At Penn State, I have taught one lower-level and one upper-level undergraduate courses. In my Soc 005: Social Problems class, I received an average rating of 6.7/7 from student evaluations. I aimed to guide students through the process of taking in contradictory information and using principles of sociology (i.e. a “sociological imagination”) to form conclusions and their own opinions about society. In my Soc 470: intermediate Social Statistics course, I received an average rating of 6.4/7. My two main goals for this class were to 1) Give students the basics of statistics which they can later build upon if they wish, and 2) Help students evaluate statistics they hear on the news, in media, or otherwise in their everyday life.

At Penn State, I have taught one lower-level and one upper-level undergraduate courses. In my Soc 005: Social Problems class, I received an average rating of 6.7/7 from student evaluations. I aimed to guide students through the process of taking in contradictory information and using principles of sociology (i.e. a “sociological imagination”) to form conclusions and their own opinions about society. In my Soc 470: intermediate Social Statistics course, I received an average rating of 6.4/7. My two main goals for this class were to 1) Give students the basics of statistics which they can later build upon if they wish, and 2) Help students evaluate statistics they hear on the news, in media, or otherwise in their everyday life.

David Nolin, Ph.D.

Penn State University
Postdoctoral Scholar: Shenk Lab, Department of Anthropology
Faculty Affiliate: Population Research InstituteCenter for Human Ecology

I am an evolutionary cultural anthropologist with methodological expertise in biostatistics, social network analysis, and demography, and a theoretical specialization in human behavioral ecology. My field research focuses on cooperative institutions in the traditional fishing and whaling village of Lamalera, Indonesia. My current work in the Shenk Research Group is a cross-cultural study of marital assortment by wealth in small-scale societies and how such assortment contributes to persistent inequality.

Current Work


  1. The evolution of human sociality and cooperation, especially as manifested in social networks of cooperative production and food sharing.
  2. The origins of and persistence of inequality in small-scale societies and its relationship to social institutions such as marriage and inheritance.
  3. The evolutionary demography of human marriage and reproduction, especially marriage delay and fertility decline.

Whaling, Sharing, and the Behavioral Ecology of Cooperation

Since 1997 I have spent nearly two years conducting field research in the traditional whaling and sea-hunting village of Lamalera, Indonesia, where I study how cooperative institutions are organized and how cooperatively acquired common-pool natural resources are managed and distributed. A combination of large-prey hunting and high-variance subsistence has made the village an ideal field site for studying cooperative subsistence behavior and human-environment interactions. I am especially interested in how cultural institutions and systems of norms can provide solutions to cooperative dilemmas and the problems posed by collective action. As a human behavioral ecologist, I am also interested in investigating the adaptive mechanisms that underpin human cooperative behavior.

This research relies heavily on social network statistics and modeling to test hypotheses about the organization of cooperative institutions and networks of social support. The results of this research show that several different adaptive mechanisms each explain part of the variation in cooperative behavior and that the underlying hypotheses are not mutually exclusive: kinship, reciprocity, and signaling all play a role in shaping patterns of cooperation and support. However, evolutionary mechanisms do not tell the whole story: social institutions, especially patrilineal kinship, corporate groups, and a complex system of norms governing harvest distributions all contribute to the maintenance of cooperation in this setting. Results from this work can be found in Current AnthropologyHuman Nature, and Evolution and Human Behavior.

Evolutionary Demography of Marriage and Reproduction

My demographic research focuses on the ecological factors that influence the onset and timing of reproduction in humans. My recent collaborative work with John Ziker (Anthropology, Boise State) has focused on demographic modeling of the abrupt decline in fertility in his field site of Ust’-Avam in central Siberia following the fall of the USSR. Over a ten-year span the population total fertility rate (TFR) fell from five to one. We were able to show that this precipitous fall in fertility is likely due to a cessation of reproduction in the face of economic and ecological uncertainty following the collapse of the USSR. Results from this collaborative work have recently been published in Human Nature and Sustainability Science.

I use similar methods to investigate marriage delay in Lamalera. This community displays several peculiar demographic features for a subsistence fishing and whaling village, including a very late age of marriage (31 for men and 29 for women), a high rate of female celibacy, and a surprising number of children entering the clergy. This project uses historical demographic methods to analyze these trends in over a century’s worth of church parish records from Lamalera. Borrowing from life history and ecological constraints theory, I relate these demographic trends to the changing socioecology of the village and the effects of household composition and sibling competition on life history outcomes.

Origins and Persistence of Social Inequality in Small-Scale Societies

Since 2007 I have been involved in a Santa Fe Institute initiative studying the origins and persistence of inequality in small-scale societies. Through a series of SFI-hosted workshops, the initial project focused on the role intergenerational transmission of wealth plays in creating and maintaining wealth inequalities. This project pooled together data from 21 different societies (including Lamalera) to examine how wealth inequality was patterned cross-culturally with results published in Science and Current Anthropology. Our Shenk Lab project on marital assortment in small-scale societies, described above, is an extension of this earlier work.

Since receiving my Ph.D. in 2008 I have taught at several institutions, including the University of North Carolina, Duke University, the University of Cincinnati, the University of California at Davis, Boise State University, and the University of Missouri. Because human behavioral ecology sits at the intersection of biological and cultural anthropology, I have taught courses from both of these subdisciplines. I also have extensive experience teaching statistics and methods, including social statistics, social network analysis, and field methods and research design. For four summers I co-taught a faculty-level workshop on Statistics in Ethnographic Research for the National Science Foundation. I have also mentored several graduate students in R-programming and statistics.

Courses Taught

Undergraduate, Lower Division

  • Introduction to Cultural Anthropology
  • Human Evolution and Adaptation
  • Ecology, Nature, and Society

Undergraduate, Upper Division

  • Human Behavioral Ecology
  • Kinship and Social Organization
  • Economic Anthropology
  • Hunter-Gatherers
  • Quantitative Field Methods
  • Cultures of Southeast Asia


  • Adaptation and Human Behavior
  • Statistical Methods in Anthropology
  • Human Cooperation in Evolutionary Perspective

Faculty Seminars & Workshops

  • Advances in the Theory and Method of Social Network Analysis
  • Statistics in Ethnographic Research

Other Potential Classes

  • Statistical Analysis of Social Networks
  • Materials and Methods of Demography
  • Social Evolution and Political Complexity

Nolin, D. and Ziker, J. (2016) Reproductive responses to economic uncertainty: fertility decline in post-Soviet Ust’-Avam, Siberia. Human Nature 27: 351-371.

Ziker, J., Rasmussen, J., and Nolin, D. (2016) Indigenous Siberians solve collective action problems through sharing and traditional knowledge. Sustainability Science 11: 45- 55.

Ziker, J., Nolin, D., and Rasmussen, J. (2016) The effects of wealth on male reproduction among monogamous hunter-fisher-trappers in Northern Siberia. Current Anthropology 57: 221-229.

Nolin, D. (2015) Disaggregating whom from how much. Current Anthropology 56:722-723. (Comment on: Kasper, C. and Borgerhoff Mulder, M. Who helps and why? Cooperative networks in Mpimbwe.)

Nolin, D. (2012) Food-sharing networks in Lamalera, Indonesia: Status, sharing, and signaling. Evolution and Human Behavior 33: 334-345.

Nolin, D. (2011) Kin preference and partner choice: patrilineal descent and biological kinship in Lamaleran cooperative relationships. Human Nature 22: 156-176.

Nolin, D. (2010) Food-sharing networks in Lamalera, Indonesia: Reciprocity, kinship, and distance. Human Nature 21:243-268.

Projects in our lab focus on three areas:


The evolution of inequality and social complexity.


The evolutionary demography of human fertility.


Kinship, marriage and family systems inevolutionary perspective.