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Promiscuous primates engage in same-sex genital interactions
Geoff R MacFarlane1, Paul L Vasey2
1School of Environmental and Life Sciences, University of Newcastle, Australia.
Behavioural Processes
|March 2, 2016
Summary
Same-sex genital interactions (SSGIs) in primates are more common in promiscuous species. These behaviors may be a byproduct of increased sexual activity, potentially serving social functions.
Area of Science:
- Primate Ethology
- Evolutionary Biology
- Behavioral Ecology
Background:
- Same-sex genital interactions (SSGIs) are observed in primates but their evolutionary persistence is unclear.
- SSGIs appear counterintuitive to reproductive goals, posing an evolutionary puzzle.
Purpose of the Study:
- To investigate the relationship between mating systems, promiscuity, and the frequency of SSGIs in primates.
- To test the hypothesis that SSGIs are more frequent in promiscuous species.
Main Methods:
- Comparative analysis of SSGIs across different primate mating systems (unimale vs. multimale).
- Correlation analysis between SSGIs and indicators of promiscuity (relative testes mass).
- Statistical controls for same-sex partner availability.
Main Results:
- SSGIs were more frequent in multimale mating systems compared to unimale systems for both sexes.
- Both male and female SSGIs showed a positive correlation with relative testes mass, an indicator of promiscuity.
- Results remained consistent after controlling for the availability of same-sex partners.
Conclusions:
- SSGIs in primates may be a neutral byproduct of selection favoring increased promiscuous sexual activity.
- These interactions could be co-opted for adaptive social functions in certain primate species.