• Stacy Rosenbaum

    Department of Anthropology | University of Michigan

    I am a behavioral ecologist who studies the evolutionary causes and consequences of social behavior. My empirical work to date has primarily focused on a wild population of mountain gorillas in the Great Lakes region of Africa. This population has been monitored for 50 years, which provides unparalleled opportunities to understand how variation in ecological and social environments influences reproductive success and life history patterns in a long-lived mammal. I use behavioral, genetic, and hormonal data to determine how kin discrimination, behavioral plasticity, and life history decisions interact to produce the astonishing range of variation observed in these animals’ social group structures and social relationships. The goal of my research is to gain a richer understanding of the evolution of mammalian sociality generally, and the hominid lineage specifically.


    In addition to my research on gorillas, I also work on complementary research questions about primate evolution, sociality and health, using the Cebu Longitudinal Health and Nutrition Survey (humans), and data collected for the Amboseli Baboon Project (savannah baboons), via collaborations with Dr. Christopher Kuzawa at Northwestern University, and Dr. Beth Archie at University of Notre Dame.


    You can find a copy of my CV here.

  • Research

    Social behavior

    Humans and many other animals develop myriad social relationships across the course of their lifetimes. I study how these relationships develop and are maintained, what their consequences are for participants, and how individual relationships impact evolutionary dynamics.


    Social relationships have many physiological correlates. For example, hormones and social behavior work in complex feedback loops. I study how relationships and physiology impact one another, and how their interactions affect health, longevity, and reproductive success.

    Methods development

    Studying wild primates, especially critically endangered species, comes with many methodological challenges. I work on improving existing tools, and developing new ones, to non-invasively measure a variety of physiological parameters.

  • Publications

    Peer Reviewed Publications

    Lea A* & Rosenbaum S* (2020). Understanding how early life effects evolve: Progress, gaps, and future directions. Current Opinion in Behavioral Sciences, in press.


    Gettler LT, Boyette A, & Rosenbaum S (2020). Broadening perspectives on the evolution of human paternal care and fathers' effects on children. Annual Review of Anthropology, in press.


    Kuzawa CW, Adair L, Bechayda SA, Borja JRB, Carba DB, Duazo PL, Eisenberg DTA, Georgiev AV, Gettler LT, Lee NR, Quinn EA, Rosenbaum S, Rutherford J, Ryan C, & McDade TW (2020). Evolutionary life history theory as an organizing framework for cohort studies: Insights from the Cebu Longitudinal Health and Nutrition Survey. Annals of Human Biology, DOI: 10.1080/03014460.2020.1742787.


    Eckardt W, Stoinski TS, Rosenbaum S, & Santymire RS (2019). Social and ecological factors alter stress physiology of Virunga mountain gorillas (Gorilla beringei). Ecology & Evolution, DOI: 10.1002/ece3.5115.


    Rosenbaum S & Gettler LT (2018). With a little help from her friends (and family) I: the ecology and evolution of non-maternal caretaking in mammals. Physiology & Behavior, 193, 1-11.


    Rosenbaum S & Gettler LT (2018). With a little help from her friends (and family) II: the behavior and physiology of non-maternal caretaking in mammals. Physiology & Behavior, 193, 2-24.


    Rosenbaum S, Vigilant L, Kuzawa CW, & Stoinski TS (2018). Caring for infants is associated with increased reproductive success for male mountain gorillas. Scientific Reports, 8:15223.


    Rosenbaum S, Gettler LT, McDade T, Augustin S, & Kuzawa CW (2018). Does men’s testosterone ‘rebound’ when dependent children grow up, or when pair bonds end? A test in Cebu, Philippines. American Journal of Human Biology, e23180.


    Rosenbaum S, Gettler LT, McDade TW, Belarmino NM, & Kuzawa CW (2018). The effects of collection and storage conditions in the field on salivary testosterone, cortisol, and sIgA. Annals of Human Biology, DOI: 10.1080/03014460.2018.1495263.


    Gettler LT, Kuo P, Rosenbaum S, Avila J, McDade T, & Kuzawa CW (2018). Sociosexuality, testosterone, and life history status: prospective associations and longitudinal changes among men in Cebu, Philippines. Evolution and Human Behavior, DOI: 10.1016/j.evolhumbehav.2018.11.001.


    Rosenbaum S, Vecellio V, & Stoinski TS (2016). Observations of severe and lethal coalitionary attacks in wild mountain gorillas. Scientific Reports, 6, 37018.


    Eckardt W, Stoinski TS, Rosenbaum S, Umuhoza MR, & Santymire R (2016). Characterizing stress physiology in Virunga mountain gorillas. Conservation Physiology, 4, cow029.


    Rosenbaum S, Hirwa JP, Silk JB, Vigilant L, & Stoinski TS (2016). Infant mortality risk and paternity certainty are associated with postnatal maternal behavior toward adult male mountain gorillas. PLoS One, DOI: 10.1371/journal.pone.0147441.


    Rosenbaum S, Hirwa JP, Silk JB, & Stoinski TS (2016). Relationships between adult male and maturing mountain gorillas persist across developmental stages and social upheaval. Ethology, 122, 134-150.


    Rosenbaum S, Maldonado-Chapparo AA, & Stoinski TS (2015). Group structure predicts variation in proximity relationships between male-female and male-infant pairs of mountain gorillas. Primates, 57, 17-28.


    Rosenbaum S, Hirwa JP, Silk JB, Vigilant L, & Stoinski TS (2015). Male rank, not paternity, predicts male-immature relationships in mountain gorillas. Animal Behaviour, 104, 13-24.


    Rosenbaum S, Silk JB, & Stoinski TS (2011). Male-immature relationships in multi-male groups of mountain gorillas. American Journal of Primatology, 71, 1-10.


    Stoinski TS, Rosenbaum S, Ngaboyamahina T, Vecellio V, Ndagijimana F, & Fawcett K (2009). Patterns of male reproductive behavior in multimale groups of mountain gorillas: examining theories of reproductive skew. Behaviour, 146, 1193-1215.


    Stoinski TS, Vecellio V, Ngaboyamahina T, Ndagijimana F, Rosenbaum S, & Fawcett K (2009). Proximate factors influencing dispersal decisions in male mountain gorillas. Animal Behaviour 77, 1155-1164.


    *Authors contributed equally

    In Progress (available upon request)

    Rosenbaum S, Eckardt W, Stoinski TS, Kuzawa CW, & Santymire RS (in revision). Validation of an androgen enzyme immunoassay as a measure of fecal testosterone and 5a-dihydrotestosterone metabolites in wild male mountain gorillas (Gorilla beringei)


    Rosenbaum S, Kuzawa CW, McDade TW, Avila J, Bechayda S, & Gettler LT (in revision). Facultative fatherhood? Testing the hypothesis of paternal-alloparental tradeoffs in Cebu, Philippines.

    Other Publications

    Rosenbaum S, Stoinski TS, & Santymire R. Urinary androgens, dominance hierarchies, and social group structure among wild male mountain gorillas. In Chimpanzees in context: a comparative perspective on behavior, cognition, conservation, and welfare (Hopper L & Ross S, eds.). University of Chicago Press. Book in press, anticipated fall 2020.


    Rosenbaum S (2018). Offspring defense. In Encyclopedia of Evolutionary Psychological Science (Shackelford TK & Weekes-Shackelford VA, eds.). Springer. DOI: 10.1007/978-3-319-16999-6_1904-1.

  • Current projects

    Special theme issue of Physiology & Behavior: Evolutionary perspectives on non-maternal care in mammals: physiology, behavior, and developmental effects.

    In most mammal species, only mothers care for young. However the exceptions, including humans, are of particular theoretical importance for our understanding of the evolution of sociality and of reproductive strategies. Lee Gettler and I co-guest edited a special journal issue on the physiology and behavior of non-maternal caretaking in mammals, The issue contains a wide variety of empirical, theoretical, and review/synthesis papers from diverse fields, including neurobiology, psychology, anthropology.


    It's out! You can find the link to the full issue here.

    Evolutionary consequences of socioecological novelty

    Mountain gorillas are a rare conservation success story, and their growing population has brought increased inter-group contact, potentially evolutionarily-novel group structures, and expansion into new, higher-elevation habitat. I am working with Drs. Tara Stoinski, Rachel Santymire, and Winnie Eckardt to understand how the animals respond to socio-environmental novelty, and use this to generate data-driven hypotheses linking emerging conditions to evolutionary outcomes at the individual, group, and population levels. In addition to its clear theoretical implications, especially in a world where virtually all organisms are experiencing the effects of rapid anthropogenic change, this research has immediate conservation implications for endangered mountain gorillas.

    Social behavior, adaptive response, and developmental constraints

    There is a large body of research on the connections between early life conditions (e.g. environmental factors like resource abundance, but also social factors such as caregiving environments) and later-life outcomes . Are the downstream outcomes adaptive responses that maximize lifetime fitness (e.g. the predictive adaptive response hypothesis), or are they simply the result of constraints imposed by environmental realities during development (e.g. the developmental constraints hypothesis)?


    Prior research in this area has focused heavily on epigenetic and physiological mechanisms, and has not yet leveraged the fundamental role that behavior generally, and social behavior specifically, may play. Initially, I am focusing on the Amboseli baboon population, in collaboration with Dr. Beth Archie. The baboons’ high environmental variability, male dispersal, and strong female dominance hierarchies make them an ideal system to study how social variables interact with ecological ones, and how the relationship between early life experiences and later outcomes is mediated by social bonds and intraspecific competition.

    Reproductive strategies and steroid hormones in non-seasonal breeders

    There is an extensive body of literature on the endocrine system switches that occur as seasonally-breeding organisms shift from mating to parenting effort and back again (aka the Challenge Hypothesis). The Challenge Hypothesis is a powerful framework for understanding hormonal mechanisms and reproductive effort in some species, but its predictive power is limited in non-seasonal breeders, and it treats “mating effort” and “parenting effort” as monoliths rather than the complex suite of behaviors each actually represents. In species such as mountain gorillas and humans, non-seasonal breeding is combined with extended offspring development, during which males offer both direct and indirect care. Organisms like these offer ideal opportunities to understand how hormonal mediators work when competing needs must be balanced.


    Using longitudinal behavioral and hormonal data from both gorillas and humans, I am writing a series of papers that explore how steroid hormones are related to intra- and inter-individual variation in male reproductive strategies, including caretaking. Across the two species, these papers address hypotheses about (for example) the effect alloparental care has on males’ testosterone profiles, and how testosterone profiles respond to the changes in caretaking behavior that occur as offspring age and become less reliant upon intensive care.

    Cryptic puberty as a life history stage

    Preliminary analyses of longitudinal hormone metabolite and behavioral data suggest that male gorillas initiate testicular production of sex steroids many years prior to the onset of their secondary sex characteristics. This finding raises interesting questions about the possible functions of this period as a life history stage and reproductive tactic in this species. This project provides the first detailed characterization of the timing of sexual maturation in wild mountain gorillas, to determine whether males are using a previously undetected strategy of “cryptic” puberty. After describing the basic phenomenon, I will use available hormone, demographic, behavioral, and life history data to test hypotheses about how social environments during development might regulate the appearance and timing of this life history stage.

    Non-invasive body composition measurement

    Even though measures of body composition (i.e. the ratio of lean tissue to adipose tissue) are crucial to answering a host of questions about development, health, competitive ability, and reproductive potential, field scientists rarely use them because of the difficulty of measurement in wild animals. Building on the work of Melissa Emery-Thompson and colleagues, we are directly validating a body composition measurement technique that relies solely on urine. The long-term goal is to build predictive equations that field scientists can use to estimate body composition in each of the four great ape species easily, cheaply, and accurately. Herman Pontzer is a collaborator on this project.

    Hormone metabolite identification using HPLC/MS

    Non-invasive endocrine analyses require measuring hormone metabolites, rather than native hormone. There are many biological and laboratory validations required to be certain that the measured metabolite accurately reflects the hormone(s) of interest. Working with colleagues at the Feinberg School of Medicine and the Smithsonian Conservation Biology Institute, we are developing a protocol to isolate and identify metabolites of interest in hormone samples obtained from wild mountain gorilla feces. Both the protocol itself and the descriptive results are applicable to a wide variety of research questions and projects.

  • Teaching


    How Humans Evolved (winter 2020 & fall 2021)

    Grant Writing for the Life Sciences (winter 2020)

    Department of Anthropology, University of Michigan

    Introduction to Human Evolution

    Department of Anthropology, UCLA

    Guest lectures

    Sex differences and convergences in socioendocrine mediation of life history strategies

    Department of Comparative Human Development, University of Chicago

    The biological origins of xenophobia

    Department of Anthropology, Northwestern University

    The evolutionary origins of friendship and family bonds in primates

    Department of Anthropology, Northwestern University

    Behavior and physiology research methods in wild and captive animal populations

    Department of Psychology, DePaul University

    Intersections of science and conservation policy

    Department of Psychology, DePaul University

    Darwinian medicine: senescence and genetic disease

    Department of Comparative Human Development, University of Chicago

    Kinship, culture, and the puzzle of human ultrasociality

    Department of Comparative Human Development, University of Chicago

    The behavior and physiology of male parenting: mountain gorillas, marmosets, and stay-at-home dads

    Department of Psychiatry and Behavioral Neuroscience, University of Chicago

    Paternal care in hominids

    Department of Anthropology, Santa Monica College

    Course Reader

    Evolution & Human Sexuality

    Human Behavioral Ecology

    Models of Cultural Evolution

    Primate Behavior Non-Human to Human

    Survey of Biological Evolution

    Great Adaptations: Origins of Complexity in Nature

    Department of Anthropology, UCLA

  • Affiliations

    Past and present

  • Science communication

    The Planetary Laboratory

    Current K-12 science teaching practices often limit kids' science exposure to out-of-date materials with little obvious relevance to the world children see around them. I am part of The Planetary Laboratory team, which is working to transport science from field sites, laboratories, and universities, into the classroom. Our NSF-supported project is helping teachers and kids learn how scientists solve problems, and helping scientists reach--and learn from--teachers and kids.

    General interest writing

  • Opportunities

    Current openings in my lab

    Prospective graduate students

    I am always happy to hear from potential graduate students or postdocs. Information about the department and the graduate school application process can be found here, but please contact me directly if you are a highly qualified candidate who plans to apply. Priority will be given to students with prior field and laboratory experience, and who have a strong interest in theory-driven questions.

  • Contact me