May 3 (UPI) -- Biologists and conservation scientists have long been operating under the assumption that inbreeding should be avoided at all costs, but a new survey -- published Monday in the journal Nature Ecology and Evolution -- suggests mating with relatives isn't always bad.
If it were, researchers contend, animals would be trying a lot harder to avoid inbreeding.
"People assume that animals should avoid mating with a relative when given the chance," lead study author Raïssa de Boer said in a news release.
"But evolutionary theory has been telling us that animals should tolerate, or even prefer, mating with relatives under a broad range of conditions for more than four decades," said de Boer, a researcher in zoology at Stockholm University in Sweden.
For the survey, scientists compiled and synthesized findings from 139 experimental studies involving 88 animal species. The results of different studies, conducted over four decades, showed animals rarely avoid mating with relatives.
"Animals don't seem to care if their potential partner is a brother, sister, cousin or an unrelated individual when they are choosing who to mate with," said study co-author Regina Vega Trejo, a researcher at Stockholm University.
The authors of the new survey also looked at studies measuring inbreeding avoidance in humans and compared the results to similar experiments involving animals.
"We compared studies that asked if humans avoid inbreeding when presented with pictures of faces that were digitally manipulated to make the faces look either more or less related to studies that used similar approaches in other animals," de Boer said.
"Just like other animals, it turns out that there is no evidence that humans prefer to avoid inbreeding," de Boer said.
The survey results show inbreeding avoidance is far from a given. In future studies, scientists said they hope to more identify the influence of cognitive and ecological factors on inbreeding avoidance.
Wildlife managers and conservation scientists should continue to monitor and take steps to bolster genetic health for species facing declines in population size, according to the researchers.
But when crafting conservation plans, the researchers suggest less emphasis should be placed on mate choice.
"A primary goal of conservation efforts is to maintain genetic diversity, and mate choice is generally expected to achieve this goal," said co-author John Fitzpatrick, zoologist at the University of Stockholm. "Our findings urge caution in the application of mate choice in conservation programs."