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1. Mother of all bonds: Influences on spatial association across the lifespan in capuchins

   https://doi.org/10.1111/desc.13486  

   Godoy, Irene ; Korsten, Peter ; Perry, Susan E. ( February 2024 , Developmental Science)

   In humans, being more socially integrated is associated with better physical and mental health and/or with lower mortality. This link between sociality and health may have ancient roots: sociality also predicts survival or reproduction in other mammals, such as rats, dolphins, and non‐human primates. A key question, therefore, is which factors influence the degree of sociality over the life course. Longitudinal data can provide valuable insight into how environmental variability drives individual differences in sociality and associated outcomes. The first year of life—when long‐lived mammals are the most reliant on others for nourishment and protection—is likely to play an important role in how individuals learn to integrate into groups. Using behavioral, demographic, and pedigree information on 376 wild capuchin monkeys (Cebus imitator) across 20 years, we address how changes in group composition influence spatial association. We further try to determine the extent to which early maternal social environments have downstream effects on sociality across the juvenile and (sub)adult stages. We find a positive effect of early maternal spatial association, where female infants whose mothers spent more time around others also later spent more time around others as juveniles and subadults. Our results also highlight the importance of kin availability and other aspects of group composition (e.g., group size) in dynamically influencing spatial association across developmental stages. We bring attention to the importance of—and difficulty in—determining the social versus genetic influences that parents have on offspring phenotypes.

   Having more maternal kin (mother and siblings) is associated with spending more time near others across developmental stages in both male and female capuchins.

   Having more offspring as a subadult or adult female is additionally associated with spending more time near others.

   A mother's average sociality (time near others) is predictive of how social her daughters (but not sons) become as juveniles and subadults (a between‐mother effect).

   Additional variation within sibling sets in this same maternal phenotype is not predictive of how social they become later relative to each other (no within‐mother effect).

    

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2. Maternal death and offspring fitness in multiple wild primates

   https://doi.org/10.1073/pnas.2015317118  

   Zipple, Matthew N. ; Altmann, Jeanne ; Campos, Fernando A. ; Cords, Marina ; Fedigan, Linda M. ; Lawler, Richard R. ; Lonsdorf, Elizabeth V. ; Perry, Susan ; Pusey, Anne E. ; Stoinski, Tara S. ; et al ( December 2020 , Proceedings of the National Academy of Sciences)

   Primate offspring often depend on their mothers well beyond the age of weaning, and offspring that experience maternal death in early life can suffer substantial reductions in fitness across the life span. Here, we leverage data from eight wild primate populations (seven species) to examine two underappreciated pathways linking early maternal death and offspring fitness that are distinct from direct effects of orphaning on offspring survival. First, we show that, for five of the seven species, offspring face reduced survival during the years immediately preceding maternal death, while the mother is still alive. Second, we identify an intergenerational effect of early maternal loss in three species (muriquis, baboons, and blue monkeys), such that early maternal death experienced in one generation leads to reduced offspring survival in the next. Our results have important implications for the evolution of slow life histories in primates, as they suggest that maternal condition and survival are more important for offspring fitness than previously realized. 

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3. Early life adversity has long-term effects on sociality and interaction style in female baboons

   https://doi.org/10.1098/rspb.2021.2244  

   Patterson, Sam K. ; Strum, Shirley C. ; Silk, Joan B. ( February 2022 , Proceedings of the Royal Society B: Biological Sciences)

   Social bonds enhance fitness in many group-living animals, generating interest in the processes that create individual variation in sociality. Previous work on female baboons shows that early life adversity and temperament both influence social connectedness in adulthood. Early life adversity might shape sociality by reducing ability to invest in social relationships or through effects on attractiveness as a social partner. We examine how females’ early life adversity predicts sociality and temperament in wild olive baboons, and evaluate whether temperament mediates the relationship between early life adversity and sociality. We use behavioural data on 31 females to quantify sociality. We measure interaction style as the tendency to produce grunts (signals of benign intent) in contexts in which the vocalization does not produce immediate benefits to the actor. Early life adversity was negatively correlated with overall sociality, but was a stronger predictor of social behaviours received than behaviours initiated. Females who experienced less early life adversity had more benign interaction styles and benign interaction styles were associated with receiving more social behaviours. Interaction style may partially mediate the association between early life adversity and sociality. These analyses add to our growing understanding of the processes connecting early life experiences to adult sociality.

    

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4. Early life drought predicts components of adult body size in wild female baboons

   https://doi.org/10.1002/ajpa.24849  

   Levy, Emily J. ; Lee, Anna ; Long'ida Siodi, I. ; Helmich, Emma C. ; McLean, Emily M. ; Malone, Elise J. ; Pickard, Maggie J. ; Ranjithkumar, Riddhi ; Tung, Jenny ; Archie, Elizabeth A. ; et al ( September 2023 , American Journal of Biological Anthropology)

   In many taxa, adverse early‐life environments are associated with reduced growth and smaller body size in adulthood. However, in wild primates, we know very little about whether, where, and to what degree trajectories are influenced by early adversity, or which types of early adversity matter most. Here, we use parallel‐laser photogrammetry to assess inter‐individual predictors of three measures of body size (leg length, forearm length, and shoulder‐rump length) in a population of wild female baboons studied since birth.

   Using >2000 photogrammetric measurements of 127 females, we present a cross‐sectional growth curve of wild female baboons (Papio cynocephalus) from juvenescence through adulthood. We then test whether females exposed to several important sources of early‐life adversity—drought, maternal loss, low maternal rank, or a cumulative measure of adversity—were smaller for their age than females who experienced less adversity. Using the “animal model,” we also test whether body size is heritable in this study population.

   Prolonged early‐life drought predicted shorter limbs but not shorter torsos (i.e., shoulder‐rump lengths). Our other measures of early‐life adversity did not predict variation in body size. Heritability estimates for body size measures were 36%–67%. Maternal effects accounted for 13%–17% of the variance in leg and forearm length, but no variance in torso length.

   Our results suggest that baboon limbs, but not torsos, grow plastically in response to maternal effects and energetic early‐life stress. Our results also reveal considerable heritability for all three body size measures in this study population.

    

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5. Differential effects of early life adversity on male and female rhesus macaque lifespan

   https://doi.org/10.1002/ece3.10689  

   Gonzalez, Stephanie J. ; Sherer, Anthony J. ; Hernández‐Pacheco, Raisa ( November 2023 , Ecology and Evolution)

   Early life adversity predicts shorter adult lifespan in several animal taxa. Yet, work on long‐lived primate populations suggests the evolution of mechanisms that contribute to resiliency and long lives despite early life insults. Here, we tested associations between individual and cumulative early life adversity and lifespan on rhesus macaques at the Cayo Santiago Biological Field Station using 50 years of demographic data. We performed sex‐specific survival analyses at different life stages to contrast short‐term effects of adversity (i.e., infant survival) with long‐term effects (i.e., adult survival). Female infants showed vulnerability to multiple adversities at birth, but affected females who survived to adulthood experienced a reduced risk later in life. In contrast, male infants showed vulnerability to a lower number of adversities at birth, but those who survived to adulthood were negatively affected by both early life individual and cumulative adversity. Our study shows profound immediate effects of insults  on female infant cohorts and suggests that affected female adults are more robust. In contrast, adult males who experienced harsh conditions early in life showed an increased mortality risk at older ages as expected from hypotheses within the life course perspective. Our analysis suggests sex‐specific selection pressures on life histories and highlights the need for studies addressing the effects of early life adversity across multiple life stages.

    

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