Center for Behavior, Evolution, and Culture

Michele Gelfand - Tight or Loose: A Fractal Pattern of Human Difference
2018-03-12 00:00 (America/Los_Angeles)
Michele Gelfand: University of Maryland Over the past century, we have explored the solar system, split the atom, and wired the Earth, but somehow, despite all of our technical prowess, we have struggled to understand something far more important: our own cultural differences. Observing the wide variety of cultural permutations, people assumed for centuries that there were as many explanations for these permutations and rifts as there were examples of them. But what my research has uncovered is that many cultural differences reflect a simple, but often invisible distinction: The strength of social norms. Tight cultures have strong social norms and little tolerance for deviance, while loose cultures have weak social norms and are highly permissive. The tightness or looseness of social norms turns out to be a Rosetta Stone for human groups. Using field, experimental, computational, and neuroscience methods, I’ve found similar patterns of difference across nations, states, organizations, and social class. Tight-loose is also a global fault line: many of the conflicts we encounter spring from the structural stress of tight-loose tension. By unmasking culture to reveal tight-loose dynamics, we can see fresh patterns in history, illuminate some of today’s most puzzling trends and events, and see our own behavior in a new light. At a time of intense political conflict and rapid social change, this template shows us that there is indeed a method to the madness, and that moderation – not tight or loose extremes – has never been more needed.

Simine Vazire - Safer Science: The Credibility Revolution in Psychological Science
2018-04-02 00:00
Simine Vazire: University of California, DavisA fundamental part of the scientific enterprise is for each field to engage in critical self-examination to detect errors in our theories and methods, and improve them. Psychology has recently been undergoing such a self-examination. Psychological scientists arguably tackle one of the hardest phenomena to understand and predict: human behavior. Naturally, our data are noisy and our findings are often tentative. However, we are slowly building knowledge and making our theories more complete. The recent self-analysis has revealed several ways we can further improve our research practices to make our findings more sound. These new norms are gaining steam within psychology and beyond, making science stronger.

Amy Boddy - Life History Trade-Offs in Reproduction and Cancer
2018-04-09 00:00
Amy Boddy: University of California, Santa BarbaraLife history theory is a powerful approach to study human health and disease. However, there has been little work in applications of life history theory in cancer biology. Here I will discuss how cancer is fundamentally characterized by life history trade-offs, as cancer defense mechanisms are a major component of somatic maintenance. Using a newly curated comparative oncology dataset across a wide range of mammals, birds and reptiles, we show a negative relationship with cancer rates and body mass or lifespan. Additionally, these organismal life history traits reflect the cellular response to DNA damage assays, providing insights into potential mechanisms of cancer defense. Understanding these trade-offs in the context of organismal evolution may help explain variability we see in cancer susceptibility across human populations. Additionally, our dataset demonstrates mammals get higher rates of cancer than other vertebrates. I will discuss the constraints of internal gestation, the process of placentation and and how these reproductive processes may lead to a trade-off with cancer susceptibility.

Zoe Liberman - Birds of a Feather Flock Together: Similarity Drives Reasoning about Affiliation and Social Group
2018-04-16 00:00
Zoe Liberman: University of California, Santa BarbaraSimilarity influences myriad social relationships. From group membership to friendship, to marriage, to mere proximity, people who are similar to one another tend to be closer than people who are dissimilar. Here, I present research indicating that infants understand the importance of homophily in determining social structure: they expect people who are similar to one another to affiliate. I also explore questions about they types of similarity infants use to reason about the social world. I hypothesize that (1) similarities that have marked human social groups across evolutionary history may be attended to earliest , and (2) that different types of similarities will be most relevant for reasoning about different types of relationships (e.g., group members vs. friends vs. family members).

Matthew Lieberman - The Brain is Social by Default
2018-04-23 00:00
Matthew Lieberman: University of California, Los AngelesOur social cognitive abilities can either be thought of like a piece of software that is written on top of existing general purpose hardware or as dedicated machinery of its own. I will present six lines of research from my lab that examine the ways in which our brain is fundamentally social rather than it being one more application of more general domain-free cognitive mechanisms. In addition, some of these lines of research will present data demonstrating that even when the brain is at rest it is actively preparing and learning from the social world.

Julie Miller - Collective Behavior in a Slave-Making Ant: Coordination and Decision-Making During Raids
2018-04-30 00:00
Julie Miller: University of California, Los AngelesThe slave-making ants are social parasites that steal their workers in coordinated raids on other colonies. Their parasitic lifestyle has made these ants a model of host-parasite co-evolution, however their charismatic brood-raiding behavior is virtually unstudied. Here I explore how colonies make collective decisions when selecting a raiding site and how colonies coordinate their attack. Slave-making has independently evolved multiple times in ants, but I focused this study on one species of North American slave-maker, Temnothorax americanus. I staged raids in table-top arenas in the lab to standardize conditions and made detailed observations of individual and colony-level behaviors. I found that the success of group raids depends on the ability of slave-makers to coordinate the timing of two roles: herding and guarding the entrance. Having established that raiding is a coordination problem, I then investigated how the colony selects a raiding site in the first place. I first measured colony preferences using choice experiments, but colonies demonstrated no preference for any size-related host features. This apparent lack of preference led to a separate question: why do colonies disregard fitness-relevant host variation? Theoretical work has offered suggestions about which conditions ought to favor low-choosiness, so I empirically tested whether they are met by T. americanus colonies, specifically testing the hypotheses that slave-makers experience (1) low host encounter rates, (2) high time constrains, or (3) low variability in host quality. To test these hypotheses, observations of lab raids were combined with spatial field data on host distribution and brood phenology. These data support that raiding is constrained by both the brief window of host brood availability, particularly of the highly valuable pupae, combined with low encounter rates of host colonies in the field. Variation in host nest quality was relatively high, and thus unlikely to favor low acceptance thresholds of slave-maker colonies. The implications of these results are that slave-maker colony raiding decisions are selected to maximize the number of raids per season, and not to selectively exploit the few most profitable ones.

Cristina Moya - The Evolution and Ontogeny of Ethno-Linguistic Reasoning
2018-05-07 00:00
Cristina Moya: University of California, DavisWhile many social species are group living, linguistically or symbolically marked social groups, characterized by large repertoires of shared cultural norms and behaviours, are uniquely human. However, the evolutionary relevance and psychological underpinnings of such ethnic groups remains debated. In this talk, I will examine the possibility that the way humans learn about ethno-linguistic boundaries reveal the structure of adaptations for reasoning about these. I report on psychological and ethnographic research from the Quechua-Aymara border in the Peruvian altiplano, and cross-cultural comparative work that speak to these questions. Results reveal 1) the importance of distinguishing between functionally independent intergroup phenomena such as stereotyping and cooperation, 2) that children are prone to develop believe that linguistic boundaries are important and fixed, and 3) that cultural evolutionary processes are likely more important than genetically evolved biases in determining the form of ethnic boundaries. Further implications for models of human social evolution will be discussed.

Amy Non - Stress, Resilience, and Embodiment of Cardiometabolic Risk in Children of Hispanic Immigrants
2018-05-14 00:00
Amy Non: University of California, San DiegoHispanic immigrants represent the largest and fastest growing ethnic minority in the US. Thus, an important research focus for the future health of the US is to determine factors that influence the declining health of immigrants with more time lived in the US, and across generations. Much research has focused on the adoption of poorer health behaviors with acculturation, but less attention has focused on the role of psychosocial stress, or resilience factors, experienced by immigrant mothers or their children. Through focus groups and extensive structured interviews with Hispanic immigrant mothers and their children (aged 6-13) in Nashville, TN, we examined a range of psychosocial stress exposures, such as work-family tradeoff and limited freedom/mobility, and resilience factors, such as optimism and social support. I will also discuss results of ongoing quantitative analyses exploring hormonal and epigenetic mechanisms through which these stressors may become biologically embedded to predispose children of Hispanic descent to higher risk for cardiometabolic diseases.

P.J. Lamberson - Exploration versus Exploitation in Collective Problem Solving
2018-05-21 00:00
P.J. Lamberson: University of California, Los AngelesThe challenge of balancing between exploiting existing solutions and exploring for new ones spans problem domains from animals foraging for food to businesses searching for new revenue streams. In this talk I will discuss a simple version of this tradeoff: When tackling a complex problem, is it better for problem solvers to work in-sequence, where each problem solver exploits the progress of those that have come before them, or in-parallel where each individual explores for new solutions independently? Using a novel mathematical model of collective problem solving we prove that for a class of especially difficult problems that we call unstructured, problem solving in-parallel performs better in expectation. We then use computational simulations to examine how violating the unstructured assumption can lead in-sequence problem solving to be superior. This is joint work with ULCA postdoctoral fellow John Lang.

Jim Sidanius - Social Dominance Theory and the Dynamics of Gendered Prejudice
2018-06-04 00:00
Jim Sidanius: Harvard UniversityUsing Social Dominance and evolutionary theory as theoretical frameworks, we argue for a model entitled the Theory of Gendered Prejudice (TGP), which in broad terms, suggests that arbitrary-set discrimination must be understood as an inherently gendered phenomenon. Employing multiple methodologies, I argue that: 1) In general, males will display higher levels of xenophobia, discrimination, social predation, and social dominance orientation than will females, everything else being equal. 2) Males will tend to be both the primary perpetrators, and the primary victims of arbitrary-set discrimination. 3) The motives for outgroup discrimination are somewhat different for males and females.

Elizabeth Chrastil - Spatial Knowledge, the Environment, and Individual Differences in Navigation Ability
2018-10-01 00:00
Elizabeth Chrastil: University of California, Santa BarbaraOrienting oneself in novel environments, as well as finding and remembering the locations of resources, is critical for human and animal existence. Despite the importance of this skill, getting around is easy for some people, while others struggle. Working at the interface between immersive virtual reality and neuroimaging techniques, my research demonstrates how these complementary approaches can inform questions about how we acquire and use spatial knowledge. In this talk, I will share emerging research about the relationship between humans and the environment during navigation, centering on three main themes: 1) how we learn new environments, 2) the type of spatial information we learn from environments, and 3) how individuals differ in their spatial abilities, including sex differences. This talk will integrate these behavioral and neuroimaging studies with an understanding of how the environment shapes our navigational abilities to inform new frameworks of spatial knowledge.

Michael Rescorla - Foundations of Cognitive Science: Mental Representation
2018-10-08 00:00
Michael Rescorla: University of California, Los AngelesJust as the heart serves to pump blood and the stomach serves to digest food, one of the mind’s principal functions is to represent the world. For instance, I have various beliefs about Barack Obama: that he was once president of the United States, that he is married to Michelle Obama, and so on. These beliefs represent Barack Obama as being a certain way. Thus, the mind somehow reaches beyond itself to external reality, depicting the world as having certain features. In that sense, the mind is a representational organ. Traditionally, philosophers have emphasized the mind’s representational capacity as among its most important properties. Cognitive science builds upon this tradition, assigning a foundational role to mental representation when constructing theories of perception, motor control, navigation, reasoning, decision-making, planning, linguistic communication, and other core mental activities. Cognitive scientists elaborate the traditional picture of the mind as a representational organ into rigorous, empirically well-confirmed theories.

Sarah Benson-Amram - Individual, Social, and Ecological Influences on Problem-Solving Abilities
2018-10-15 00:00
Sarah Benson-Amram: University of WyomingAs urban centers all over the world have grown, biologists have struggled to explain why some species can invade and thrive despite human-induced environmental change whereas others suffer often to the point of extinction. One potential explanation is that the evolution of advanced cognitive abilities has enabled some species to exhibit more flexible behavioral responses to anthropogenic disturbances. Empirical evidence for this hypothesis is lacking, however, as it is difficult both to assess cognition in wild animals and to standardize assessments of cognition across multiple species in differing environments. The main goals of my research program are: 1) to understand the selection pressures driving the evolution of intelligence, 2) to clarify how the expression of behavioral flexibility and other cognitive abilities changes depending on the individual’s personality, the presence and identity of conspecifics, and the ecological environment, and 3) to investigate how cognition might facilitate successful adaptation to human-altered environments. In this talk, I will touch upon all three of these areas of research. I will first discuss my work examining the evolution of brain size and problem-solving abilities in a large comparative study of zoo-housed carnivores. I will then describe results from our research examining cognitive abilities in wild and captive populations of two highly successful carnivores, the spotted hyena and the raccoon. Finally, I will briefly describe some current research in our lab examining the interaction between personality and problem-solving performance in the monogamous zebra finch.

Eduardo Guerra Amorim - Migration and social organization in medieval Europe: a paleogenomic approach
2018-10-22 00:00
Eduardo Guerra Amorim: University of California, Los AngelesDespite centuries of research, much about the barbarian migrations that took place between the fourth and sixth centuries in Europe remains hotly debated. To better understand this key era that marks the dawn of modern European societies, we obtained ancient genomic DNA from 63 samples from two cemeteries (from Hungary and Northern Italy) that have been previously associated with the Longobards, a barbarian people that ruled large parts of Italy for over 200 years after invading from Pannonia in 568 CE. Our dense cemetery-based sampling revealed that each cemetery was primarily organized around one large pedigree, suggesting that biological relationships played an important role in these early medieval societies. Moreover, we identified genetic structure in each cemetery involving at least two groups with different ancestry that were very distinct in terms of their funerary customs. Finally, our data are consistent with the proposed long-distance migration from Pannonia to Northern Italy.

Daniel Benyshek - Human Maternal Placentophagy: evolutionary roots, cross-cultural occurrence, and an emerging post-industrial health trend
2018-10-29 00:00
Daniel Benyshek: University of Nevada Las VegasMaternal placentophagy, the mother’s consumption of the ‘afterbirth’ following parturition, is a ubiquitous behavior among terrestrial mammals – including non-human primates. Despite myriad hypothesized fitness-enhancing consequences of the behavior, including predator avoidance, improved lactation, enhanced care-taking behaviors, maternal analgesic effects, and the replenishment of maternal nutrients, among others, human maternal placentophagy is unknown in the cross-cultural ethnographic literature. The conspicuous absence of placentophagy in humans as a traditional cultural practice, raises interesting questions relative to its evolution in other mammals, the reasons for its apparent absence among historic and contemporary human populations, and its implications for maternal and child health in the context of an emerging placentophagy ‘alternative health’ practice among some women in post-industrial societies.

Susan Schaffnit - ‘Child marriage’ in context: understanding the drivers of early marriage in rural Tanzania
2018-11-05 00:00
Susan Schaffnit: University of California, Santa BarbaraA global campaign to end ‘child marriage’ (i.e. marriage before 18 years) has emerged over the last decade as part of growing international commitments to address gender inequities and improve female wellbeing. Proponents of this movement assert that young brides have negligible autonomy in the marriage process and that marrying under 18 years has resolutely negative impacts on wellbeing. This concern surrounding early marriage has largely proceeded without theoretical engagement with anthropologists and despite gaps in supporting evidence of harm to women. Using data collected in rural, northwest Tanzania where early marriage is common, I will (1) discuss local views on marriage, (2) test hypotheses as to why early marriage is common despite purported harm. Our findings suggest that early marriages can be understood as serving the strategic interests of both parents and daughters in some circumstances. I will discuss the generalizability of this finding and implications for the ‘end child marriage’ movement.

Jeremy Koster - Cross-Cultural Variation in the Life History of Human Foraging Skill
2018-11-19 00:00
Jeremy Koster: University of Cincinnati, OhioHumans are distinguished from other hominoids by several life history traits, including prolonged childhoods, relatively brief inter-birth intervals, and extend post-reproductive lifespans. To explain the evolution of these traits, anthropologists have hypothesized that the cognitive demands of hunting necessitate extensive learning, which promotes late maturation and inter-generational food sharing. In this analysis, my colleagues and I evaluate a key component of this conceptual model, namely that advanced hunting skill is particularly evident among middle-aged hunters. We compile data on subsistence hunting from 40 sites around the world in a sample that includes over 23,000 hunting records from approximately 1,800 individual hunters. We use multilevel modeling and a life history model to estimate the latent skill of hunters as a function of their age. On average, hunters reach their peak at approximately 31 years old. The peak is not pronounced, however, and there is cross-cultural variation in age-related skill that challenges earlier findings. These results accentuate the need for additional longitudinal data on foraging activities as a counterpoint to theoretical models of life history evolution.

Thomas J. H. Morgan - Experimental Human Gene-culture Coevolution
2018-11-26 00:00
Thomas J. H. Morgan: Arizona State UniversityThe evolution of human behavior and cognition is often studied with a combination of theory and experiment—theory is used to explore evolutionary dynamics, and generate predictions that are tested empirically. However, agent psychology is typically highly simplified and so it can remain unclear whether human behavior would produce the same evolutionary dynamics. To address this question, I describe a new method, “experimental evolutionary simulations”, that combines aspects of theoretical and empirical approaches by inserting large numbers of human participants into an evolutionary simulation. I use this approach to provide new data concerning the ability of human social learning to adapt to an unstable environment. Theory has identified different social learning strategies that are highly successful or unsuccessful in a changing environment. Experimental evidence suggests that human behavior is broadly consistent with many of these predictions and so it remains unclear how well a population of human learners would cope with environmental change. Across a series of experimental evolutionary simulations, I find that although human behavior is broadly consistent with theoretical strategies that are successful in a changing environment, this similarity is insufficient to actually buffer human populations against environmental change. I conclude that human psychology is designed for high fidelity copying and not adapting to environmental novelties. More generally I suggest that experimental evolutionary simulations are a valuable complement to existing methods in the evolutionary study of mind and behavior.

Amy Parish - Reflections on Our Closest Living Relatives and Ourselves: Lessons from the Bonobo Sisterhood
2018-12-03 00:00
Amy Parish: University of Southern California“Oooooh, I want to be like youuuu, …walk like you, talk like you, tooooo.” So goes the lament of Louie, the Orangutan King in “The Jungle Book”. He wishes he could be like a human. In contrast, Mogli, the human boy in the movie, thinks of himself as just one of many types of forest animal. The movie represents a conflict in humanity’s search for self-identity. What really separates “man” from “animal”, if indeed there is such a separation? We are desperate to know. Approximately 200 species including humans belong to the Primate mammalian order. Like all animals, they are faced with the problems of how to survive, breed and rear offspring. The mating behavior of the apes is particularly complex and fascinating. Chimpanzee (Pan troglodytes) societies are typically characterized as physically aggressive, male-bonded and male-dominated. Their close relatives, the bonobos (Pan paniscus), differ in fascinating and significant ways. For instance, female bonobos bond with one another, form coalitions, and dominate males. Both species are equally “man’s” closest relative. How do these findings change our views of our evolution and ourselves? This talk explores the sexual and social behavior of one of our closest living relatives: the bonobo.

Dan Blumstein - The Sound of Fear
2019-01-07 00:00
Dan Blumstein: University of California, Los AngelesWhat makes certain sounds scary? I will describe insights gained from over three decades of studying alarm calls and fear screams in marmots (which are large, mostly-alpine, ground squirrels) throughout the northern hemisphere. Fear screams are remarkably similar across taxa and they seem to be particularly evocative to many species. My studies of non-humans suggest that it is the noise and non-linearities in them that is what evokes negative emotions and heightened responses in those hearing them. I formalize this in ‘the non-linearity and fear hypothesis’ and discuss my tests of the hypothesis in studies of marmots, birds, film soundtracks, and humans. The sound of fear is non-linear.

Angela Garcia - The Embodiment of Stress: Do diurnal cortisol-immune interactions and parasitic infection moderate social influences on health among immigrant women on Utila?
2019-01-14 00:00
Angela Garcia: Arizona State University Cardiometabolic diseases (e.g. heart disease and diabetes) are the leading cause of death and morbidity worldwide. Diabetes, for example, will double in the next 30 years, with 80% of the rise occurring in middle and lower- income countries. Social, economic, and ecological landscapes often change alongside market integration and development, making it difficult to tease apart the primary agents responsible for these changes in epidemiological profiles. Further, at the population-level, there remains drastic individual variation in disease risk. Why are some individuals in a population at greater risk of poor health than others? What can an evolutionary approach offer in helping us to understand causes (and potential treatments) for current health disparities? This research seeks to address these questions by targeting three important but under-studied factors that contribute to disease risk: discrimination, psychosocial stress, and ecological variation. In this talk, I couple fieldwork and ethnography with theory from evolutionary biology (e.g. life history theory and phenotypic plasticity), biocultural anthropology (e.g. perceptions of self and the environment), and chronobiology (e.g. diurnal regulation of hormones and immune function), to examine links between social and ecological parameters of the environment, hormonal measures of stress, immune function, and risk for diabetes among Honduran immigrant women on the island of Utila.

Nandita Garud - The Bacteria Evolving Within Us
2019-01-28 00:00
Nandita Garud: University of California, Los AngelesThe human gut microbiome is comprised of a complex ecosystem of microbes that reside inside of us and play an important role in our health. With as many as a billion new mutations entering our microbiomes per day, bacterial genomes inside us have a great opportunity to evolve rapidly, unlike our own genomes, which change very little throughout our lifetimes. For us humans, this genetic dynamism is both an opportunity (e.g., enabling digestion of new foods) and a challenge (e.g. the evolution of drug resistance). Despite the potential importance of these effects, we currently know very little about if and how bacteria living in us evolve. I will present our recent work quantifying the evolutionary dynamics of ~40 prevalent species of gut bacteria. We find that gut bacteria can evolve within humans on short timescales (~6 months), but over our lifetimes resident bacteria are typically replaced by distantly related strains. These results suggest that gut bacteria can evolve on human-relevant timescales, but that there are limits to the extent of local adaptation.

Courtney Meehan - [CANCELED] The social worlds of infants, moms, and microbes
2019-02-04 00:00
Courtney Meehan: Washington State University Throughout our evolutionary history, and in much of the world today, human infancy has been characterized by a host of ancestral traits which include frequent maternal-infant contact, on-demand breastfeeding, co-sleeping, and cooperative breeding. These ancestral characteristics have, in part, supported the development of our altricial infants and enabled reproductive success in diverse environments, despite women’s narrow reproductive window and the costs associated with simultaneously rearing multiple dependent children. Here, I argue that these ancestral traits also serve as a critical pathway by which mothers and infants communicate, via microbiota, about their environment, priming the infant for the world in which he or she will be reared. Utilizing cross-cultural data on infant’s early environments and human milk composition, I characterize the diverse caregiving worlds of infants and explore how our early social environments and mothers’ life history characteristics are associated with the human milk microbiome (HMM). Human milk, once thought to be sterile, contains a diverse microbial community and as an early and consistent source of bacteria to infants, it is an important factor in the colonization of the infant gastrointestinal microbiome. Yet, the origins and role of the HMM are not yet fully understood. Our results identify multiple associations between maternal life history characteristics, our ancestral caregiving traits, and the HMM, providing initial evidence suggesting bi-directional maternal-infant communication during breastfeeding and that human milk composition may be socially-mediated.

Melanie Martin - Human infant feeding: evolved strategies, individual optimums, and public health
2019-02-11 00:00
Melanie Martin: University of WashingtonAcross past and present human populations, breastfeeding and weaning practices have been demonstrably varied. Though this variation is largely influenced by ecological and socioeconomic factors, comparative primate and human biological and cross-cultural evidence further suggests that flexible mixed-feeding is an evolved human strategy. In this talk, I review the differences in infant energetic needs and maternal time, physical, and reproductive constraints that favor individual optimums for exclusive and total breastfeeding durations. I draw
on my work with indigenous Tsimane and Qom/Toba families to illustrate that (1) early (“suboptimal”) mixed-feeding can still be compatible with long-term, intensive breastfeeding and (2) that more discreet measures of feeding trajectories and their multidirectional effects on growth and other biological processes should be considered in assessing relationships to health outcomes. In closing I emphasize that these positions are not incompatible with current age-delineated feeding recommendations, which are essential for uniform public health messaging
and related policy development. Instead, an evolutionary and biocultural perspective may inform parallel dialogs among families and health care providers that acknowledge diverse needs and circumstances in shaping individual feeding optimums.

Josh Snodgrass - Life history tradeoffs between childhood growth and immune function among Shuar forager-horticulturalists of Amazonian Ecuador
2019-02-25 00:00
Josh Snodgrass: University of OregonImmune function is an energetically costly physiological activity that can divert calories and other resources away from less immediately essential life history functions such as growth. However, direct evidence for immune-related tradeoffs among humans remains sparse. In this talk, I discuss longitudinal research among Shuar children (4-11 years old) that uses high-resolution linear growth data and dried blood spot samples for four immune measures. This research documents consistent negative effects of immune function on growth, with children experiencing up to 49% growth reduction during periods of mildly elevated immune activity. Additional findings show that tradeoffs are immunologically and temporally diverse, and also document a particularly detrimental impact of acute inflammation on growth though these inflammation-related tradeoffs with growth are buffered by body fat. I conclude by discussing the role of immune-related tradeoffs in driving patterns of human growth faltering, developmental metabolic plasticity, and life history evolution.

Dan Hruschka - What does it mean to replicate studies in a cultural species?
2019-03-04 00:00
Dan Hruschka: Arizona State University Replicating a study among our fellow humans requires a researcher to interact with study participants according to protocols that are comparable with previous studies. However, thanks to humanity’s rich capacity for cultural learning, it can be challenging to identify what counts as a “comparable protocol” across different human groups. Specifically, diverse culturally learned capacities, motivations, symbolic connections, and expectations for appropriate social interactions can make some protocols impossible to implement directly across cultures while rendering the results of other “workable” protocols nearly impossible to interpret. I used examples from our work studying the social determinants of giving to illustrate: (1) the extent of this problem, and (2) how overcoming such challenges can tell us about our tacit models of how humans should think and behave. In this way, such efforts at translation are not just a methodological exercise, but can also inform our models of human psychological and behavioral diversity.

Raziel Davison - Evolutionary Retrospectives on the Human Life History Trajectory
2019-03-11 00:00
Raziel Davison: University of California, Santa Barbara We investigate human life history evolution by comparing smallscale subsistence societies and chimpanzees to identify the roles that fertility and mortality play in driving population-level fitness differences. We discuss differences in the selection pressures facing individuals of different ages and to make inferences about the trajectory of human life history evolution. Most human populations are growing but post-reproductive survival decouples population growth from lifespan, with high fertility driving rapid growth in some societies and low fertility balancing longevity to maintain near-stationarity in others. Chimpanzee declines are decoupled from fertility because mortality attrition limits higher potential fertility contributions. Selection pressures suggest that variable child survival likely regulated human population dynamics over evolutionary history and may reflect bet-hedging costs of high fertility, with quality/quantity trade-offs constraining the evolution of slower life histories. Common stationarity conditions may represent invariant allometry of chimpanzee and human life histories. Among humans, production and knowledge transfers constituting fitness contributions of post-reproductive adults part the veil of selection to favor long post-reproductive lifespans, but in chimpanzees transfers
are limited and reproductive senescence tracks mortality closely.

Ashley Hazel - Ecological dynamics of sexually transmitted infections among Namibian pastoralists
2019-04-01 00:00
Ashley Hazel: Stanford UniversityPopulations that are dependent upon physical environments for their immediate livelihoods utilize subsistence strategies that are both well adapted to predictable environmental variability (e.g., seasonality) and resilient to unpredictable shocks (e.g., drought). Livelihood strategies that entail high degrees of mobility typically have temporal and spatial heterogeneities in social contact, which influences infection dynamics for pathogens that require prolonged or repeated contact for transmission, such as sexually transmitted infections (STIs) or tuberculosis.
In this talk, I present my work on the epidemiology of two STIs—HSV2 and gonorrhea—among a group of semi-nomadic pastoralists in Kaokoveld Namibia, where sexual-partner concurrency functions not just as an STI risk factor but, crucially, as an ecological strategy. I find that extreme geographical remoteness is associated with a higher HSV2 (viral) transmission rate. In contrast, ephemeral population density and social aggregation are associated with higher gonorrhea (bacterial) prevalence. Furthermore, both predictable and unpredictable climate variation influenced sexual-networks, which has important implications for the impending effects of climate change.

Alexandra Binder - Epigenetics and the Developmental Origins of Health and Disease
2019-04-08 00:00
Alexandra Binder: University of California, Los AngelesThere is extensive epidemiologic and experimental evidence linking early life conditions to adult health. Epigenetic modifications are suspected to play a role in mediating these associations by providing a cellular memory of gene regulation shaped by exposures during critical windows of development. In this lecture, I will discuss some of my research into the relationships between epigenetic patterns and early life predictors of adult disease susceptibility. I will highlight our recent investigations into specific patterns of DNA methylation that influence pubertal development among a longitudinal cohort of girls in Santiago, Chile. More generally, I will detail salient methodological considerations for identifying determinants of epigenetic variation in observational human studies. I will also outline generalizability and reproducibility concerns within the field of epigenetic epidemiology, and how these considerations should inform study design and the discussion of study implications.

Pam Yeh - How interactions among multiple stressors affect the ecological and evolutionary trajectories of populations
2019-04-15 00:00
Pam Yeh: University of California, Los AngelesAll natural populations deal with multiple stressors. Yet there is limited understanding of how populations are impacted by higher-order interactions — more than two stressors. In this talk I will explain my new conceptual and experimental work to examine higher-order interactions among antibiotics in bacterial populations. I will also present recent work from my group that shows bacteria likely co-opted ancient stress response mechanisms to extreme temperatures in order to deal with more recent antibiotic stresses. This co-opting avoids the need for de novo evolution of response mechanisms to antibiotics.
