When chimps seek out a mate, they look for a chimpanzee with a very different genetic makeup. Genetic opposites attract, according to researchers at Duke University.

Biologists tracked the mating behavior of chimpanzees living in Gombe National Park in Tanzania and found chimps can discern varying degrees of genetic similarity among potential mates. Chimps prefer to mate with the least similar genetically.

Scientists also found females who leave their community of extended relatives to establish a family elsewhere tend show an even stronger preference for genetically dissimilar mates than do females who remain with kin through adulthood.

Other animals avoid mating with relatives, but the ability to recognize degrees of genetic difference among non-relatives is unique.

Researchers aren't sure how chimps make the distinction; their best guess is the apes use appearance, smell or sound to make an educated guess. Scientists hope further research will further illuminate the unique ability.

The new study -- published in the journal Royal Society Open Science -- suggests the risk of inbreeding is a powerful motivating factor for chimpanzees.

It's possible, the study's authors argue, female chimps also unconsciously select the sperm of mates who are most genetically distinct.