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Abstract ObjectiveReconstructing the social lives of extinct primates is possible only through an understanding of the interplay between morphology, sexual selection pressures, and social behavior in extant species. Somatic sexual dimorphism is an important variable in primate evolution, in part because of the clear relationship between the strength and mechanisms of sexual selection and the degree of dimorphism. Here, we examine body size dimorphism across ontogeny in male and female rhesus macaques to assess whether it is primarily achieved via bimaturism as predicted by a polygynandrous mating system, faster male growth indicating polygyny, or both. MethodsWe measured body mass in a cross‐sectional sample of 362 free‐ranging rhesus macaques from Cayo Santiago, Puerto Rico to investigate size dimorphism: (1) across the lifespan; and (2) as an outcome of sex‐specific growth strategies, including: (a) age of maturation; (b) growth rate; and (c) total growth duration, using regression models fit to sex‐specific developmental curves. ResultsSignificant body size dimorphism was observed by prime reproductive age with males 1.51 times the size of females. Larger male size resulted from a later age of maturation (males: 6.8–7.8 years vs. females: 5.5–6.5 years; logistic model) and elevated growth velocity through the pre‐prime period (LOESS model). Though males grew to larger sizes overall, females maintained adult size for longer before senescence (quadratic model). DiscussionThe ontogeny of size dimorphism in rhesus macaques is achieved by bimaturism and a faster male growth rate. Our results provide new data for understanding the development and complexities of primate dimorphism.
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This content will become publicly available on August 19, 2026
Skeletal Growth Modeling for the Cayo Santiago Rhesus Macaques with Stepwise Regression Supported in CSViewer for Analysts
Growth modeling is a key aspect of statistical analysis, particularly in fields such as biology, economics, and social sciences. In primate development studies, ontogeny is a well-known phenomenon that skeletal growth tends to stop at a certain age. Bone dimension measures of over 1200 skeletal sets derived from the Cayo Santiago (CS) rhesus colony were recently collected by a collaborative effort supported through NSF grants. These measures provided a valuable resource for extending a knowledge model for primate skeletal development regarding ontogeny, and variations based on sex and matrilineal lineage. This paper presents initial results of a custom regression model proposed, as well as model comparisons with other popular models used in similar line fitting tasks. Related data analytics and visualization support as implemented in the CSViewer for Analysts system are also described.
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- Award ID(s):
- 1926402
- PAR ID:
- 10652410
- Publisher / Repository:
- Springer Nature Switzerland
- Date Published:
- Edition / Version:
- Lecture Notes in Networks and Systems
- Volume:
- 1423
- ISBN:
- 978-3-031-92601-3
- Page Range / eLocation ID:
- 341 to 352
- Subject(s) / Keyword(s):
- Primate skeletal development, Custom regression, Cayo Santiago Rhesus Macaques, CSViewer for Analysts, Knowledge model
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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