Using sex to manage social tension dates back over six million years to humans’ common ape ancestor, according to a new study.
Researchers from our Department of Psychology compared sexual behaviour within sanctuary-living bonobos and chimpanzees during times of social stress (such as after a fight or before competitive feeding).
Their aim was to understand if using sex to ease social tension is a common behavioural trait between the two sister species.
Bonobos are well known to regularly use sex to resolve disputes and repair social bonds. However, until now the role of sex in chimpanzee society has been less well understood.
The team found that both bonobos and chimpanzees used sex in similar ways to ease tension and reaffirm social bonds before feeding.
Bonobos also often had sex more after fights to repair social relations.
Chimpanzees, however, may be more likely to use other behaviours, like body kissing, after a disagreement.
Age did not influence post-fight sexual behaviour in either species. However, older apes were more likely to initiate sex before feeding, suggesting it may be a learned behaviour passed down over time.
Researchers also noted that female bonobos and male chimpanzees were more likely to initiate sex prior to feeding, but in both species, sex occurred in both hetero and homosexual combinations.
The findings provide a fascinating window into our evolutionary past, supporting the idea that using sex for social purposes can be traced back to the common ancestor humans share with apes, over six million years ago.
This is a first direct comparison of sexual behaviour in bonobos and chimpanzees, our two closest cousins. The fact that both species use sex in this way provides a fascinating window back in time, further evidencing that for humans, bonobos, and chimpanzees, our use of sex for social reasons is something we have inherited from our common ancestor.
The study took place at two African great ape sanctuaries: Lola ya Bonobo Sanctuary in the Democratic Republic of Congo, and Chimfunshi Wildlife Orphanage Trust in Zambia.
In total over 1,400 hours of observations were taken involving 53 bonobos and 75 chimpanzees, across seven months.
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Image credit: Credit Zanna Clay/ Lola ya Bonobo
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