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In reality, animals hardly care about inbreeding

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New research from researchers at Stockholm University suggests that contrary to popular belief, animals rarely develop strategies to avoid inbreeding.

Animals do little to avoid inbreeding

The idea that animals prefer to avoid mating with parents has motivated the development of hundreds of scientific studies conducted on many species. It turns out, however, that the reality is a bit more nuanced. Indeed, “evolutionary theory tells us that animals should tolerate, if not prefer, mating with parents under a wide range of conditions for more than four decades“, Observes Raïssa de Boer, researcher in zoology at the University of Stockholm.

In Nature, his team provides a summary of 139 studies of 88 different species spanning forty years of research on inbreeding in the animal world. This work reveals that there is a publication bias in favor of studies showing avoidance of inbreeding in animals. More specifically, studies highlighting a preference for a related partner are lacking in the publication folder. For the authors, this observation is mainly linked to our moral bias against inbreeding.

In fact, this meta-analysis shows that animals rarely attempt to avoid mating with parents. “They don’t seem to care if their potential mate is a sibling, cousin, or unrelated person when choosing who to mate with.“, Notes Regina Vega Trejo, lead author of the study. This conclusion agrees with the theoretical expectations of researchers: “models predict that non-kinship-biased mating should be common“, She confirms.

No need for an avoidance strategy

Naturally, we know that inbreeding can lead to an accumulation of restricted genetic characteristics within the same individuals, which increases the chances of the development of diseases or disabilities. As a rule, however, these problems occur over several generations when inbreeding is forced, intentionally or not.

In the animal kingdom, on the other hand, it can happen that the living conditions are not sufficiently conducive to inbreeding. Imagine, for example, a vast territory made up of many specimens. In this case, there is statistically less chance of stumbling upon a member of his lineage and mating with it. And there is even less chance of it happening again the next generation. As a result, the individuals do not have to develop any particular strategy to avoid it.

Likewise, if a species generates significant offspring, then the inbreeding of some individuals will not prevent it from surviving. Here again, the animals involved will therefore not need to evolve their strategy to avoid inbreeding.

Our findings help explain why many studies have failed to find clear support for inbreeding avoidance and offer a useful roadmap for better understanding how cognitive and ecologically relevant factors shape avoidance strategies. inbreeding in animals“, Continues John Fitzpatrick, co-author of this work.

Same observation in humans?

The study also looked at the prevention of inbreeding in our species. Among the studies reviewed, one involved presenting photos of potential partners to men and women, and asking them which they found most attractive. Some photos had been altered so that the face resembled the subject enough to evoke a family relationship. However, the modified photos have had the same success as the others.

So for the authors, it could even be that our own species is not better able to avoid inbreeding. “Just like with other animals, it turns out that there is no evidence that humans prefer to avoid inbreeding.“, Despite our“tendency to react with disgust to incest“, Concludes Raïssa de Boer, co-author of the study.

However, this experience shows some limitations. “Measures of mate choice in humans were outside their natural context“, Admit the researchers.


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