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Grandmaternal Caregiving is Associated with Distinct Multi-Voxel Neural Representation of Grandchildren in the Parental Motivation Circuit
Grandmaternal Caregiving is Associated with Distinct Multi-Voxel Neural Representation of Grandchildren in the Parental Motivation Circuit
Arianna Mistry1*, Elizabeth Whiteside2*, Gita Gnanadesikan1, Sarah Brosnan3, and Marcela Benítez1
*Co-first authors
1 Department of Anthropology, Emory University, 2 Baylor College of Medicine, 3 Department of Psychology, Georgia State University
Menopause–the end of reproductive function–is a critical transition in a human female’s life. Humans can live up to a third of their lives in a post-reproductive stage, which is highly unusual among primates. As research on menopause expands, evidence of a post-reproductive period has recently been observed in wild chimpanzees and estimated in captive populations of chimpanzees, gorillas, orangutans, and macaques. However, hormonal evidence remains limited, and whether other long-lived primate species exhibit similar declines in reproductive hormones and fertility is still unknown.In this study, we examined age-related effects on fecal estradiol concentrations in 22 captive female tufted capuchin monkeys (Sapajus apella) at the Georgia State University Language Research Center from 2017 to 2024 to provide evidence for the occurrence of menopause in the oldest members of a captive population. In addition to age-related hormonal changes, we investigated how aging affects the frequency of sexual soliciting, or estrus, behaviors in individuals over the age of 30 to further explore the occurrence of menopause in tufted capuchins. Comparing adult (<30 years old) and old-age (>30 years old) individuals, we found that both fecal estradiol concentrations and frequencies of estrus behaviors decline with age. Our results were further supported by a biological validation with a female who had undergone an ovariectomy. This individual showed a significant difference in preoperative versus postoperative estradiol concentration and estrus behaviors, but no significant difference between the ovariectomized condition and the old-age individuals. Our findings suggest the occurrence of menopause in old-age, captive tufted capuchins and have implications for the use of estradiol to explore menopause in other captively housed, long-lived primates. In addition to improving our understanding of capuchin reproduction, this work informs theories regarding the adaptive significance of post-reproductive lifespans and the socioecological influences on female life history patterns.
Menopause–the end of reproductive function–is a critical transition in a human female’s life. Humans can live up to a third of their lives in a post-reproductive stage, which is highly unusual among primates. As research on menopause expands, evidence of a post-reproductive period has recently been observed in wild chimpanzees and estimated in captive populations of chimpanzees, gorillas, orangutans, and macaques. However, hormonal evidence remains limited, and whether other long-lived primate species exhibit similar declines in reproductive hormones and fertility is still unknown.In this study, we examined age-related effects on fecal estradiol concentrations in 22 captive female tufted capuchin monkeys (Sapajus apella) at the Georgia State University Language Research Center from 2017 to 2024 to provide evidence for the occurrence of menopause in the oldest members of a captive population. In addition to age-related hormonal changes, we investigated how aging affects the frequency of sexual soliciting, or estrus, behaviors in individuals over the age of 30 to further explore the occurrence of menopause in tufted capuchins. Comparing adult (<30 years old) and old-age (>30 years old) individuals, we found that both fecal estradiol concentrations and frequencies of estrus behaviors decline with age. Our results were further supported by a biological validation with a female who had undergone an ovariectomy. This individual showed a significant difference in preoperative versus postoperative estradiol concentration and estrus behaviors, but no significant difference between the ovariectomized condition and the old-age individuals. Our findings suggest the occurrence of menopause in old-age, captive tufted capuchins and have implications for the use of estradiol to explore menopause in other captively housed, long-lived primates. In addition to improving our understanding of capuchin reproduction, this work informs theories regarding the adaptive significance of post-reproductive lifespans and the socioecological influences on female life history patterns.
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