In order to discover how important similarity was in forming relationships, professor Angela Bahns and her team of researchers approached over 1,500 random pairs (romantic couples, friends, and acquaintances) and surveyed them on their values, prejudices, attitudes and personality traits.
The animals do more than simply avoid mates they grew up with and are therefore likely to be related to, the study shows.
In addition to whatever means they are using to distinguish relatedness, they could also rely on timing, being pickier about their sexual partners during the part of a female's cycle when she is most likely to conceive.
Flirt, a young female chimpanzee, left her brothers and other relatives behind when she reached puberty to reproduce in a new group.
A study finds that chimps can tell genetically similar mates from more distant ones, even among unfamiliar partners.
The researchers aren't sure yet exactly how they discriminate, but it might be a best guess based on appearance, smell or sound, said senior author Anne Pusey, professor of evolutionary anthropology at Duke.