All primates share a common ancestor, naturally extending interest in aging across primate species.
All sexually reproducing organisms 'senesce,' that is, experience physiological decline with age, which can explain why old monkeys rest and sleep more than younger individuals. An explanation for the sex-based differences in aged social behavior and social networks reported in this study, however, may originate in rhesus' matrifocal social structure. Related females remain in their matriline for life while males leave their birth families at adolescence and transfer into non-related groups throughout their adult lives. Strategies for 'successful' aging, i.e. survival therefore, may vary by sex in aged rhesus.