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| Two adolescent male chimpanzees, Barron, 15, and PeeWee, 9, grooming. Photo Credit: Aaron Sandel. |
Romantic heterosexual relationships in humans may have evolved from same-sex pairings in a common ancestor of humans and chimpanzees, according to a novel hypothesis by a researcher at The University of Texas at Austin.
The prevailing explanation of heterosexual pair bonding and romantic love in humans is that it evolved from the mother-infant bond present in many mammals. In a paper published in the journal Evolutionary Anthropology, anthropology professor Aaron Sandel cites primate research — including his own decadelong studies of chimpanzees in Kibale National Park, Uganda — to propose instead that this behavior evolved in humans from same-sex pair bonding already present in a common ancestor of humans and chimpanzees.
A pair bond is a cooperative relationship between nonrelated adults that remains stable over time and includes an emotional connection, rather than being merely transactional. Chimpanzees, humans’ closest relative, do not pair bond with their mates, but adult males of the species form same-sex bonds lasting as long as 13 years.









