Talking and writing about inbreeding in humans is always a complex topic , especially with two little sisters! Jokes aside, the issue of consanguinity always brings to mind former (or not so much) monarchs , getting together with cousins and cousins to try to preserve their blood purity; to end up suffering from hereditary diseases due to the loss of genetic variability. Who would want this for their offspring?
It would be logical to think that a fact that seems to go so against the evolutionary triumph of living beings, was avoided at all costs when choosing a partner (in ecology: kin avoidance ). Well, as you can imagine, a meta-analysis (that is, a study that brings together many studies) by a group of researchers from the University of Stockholm, has proven that incest in nature is more common than it seems. And that, kings and queens aside, humans are not saved either.
In an interview for The Scientist magazine, Regina Vega-Trejo, co-author of the study, claims that “ what we found is that animals don’t seem to care about the difference. When making the decision between an unrelated individual and a related individual, they don’t care too much. […] Of course, we are analyzing many studies. I think what’s important is to keep in mind that, in 70% of the studies, they didn’t care. Of course, some avoided inbreeding, and then some preferred inbreeding. But when you do a study like this, what you really focus on is the average, and in 70% of the investigations, they didn’t care … they basically just thought about mating. “
The meta-analysis encompassed more than 40 years of research through the study of 139 experimental publications in which the preferences of various species were compared when choosing a mate, specifically, if the choice was a relative or a non-relative. It also turned out that, in some cases, depending on the conditions, the benefits of inclusive fitness of the group associated with inbreeding could lead to a preference for mating with relatives.
Finally, no significant differences were found in kinship evasion for reproduction neither between males and females nor between humans and animals. Which would mean that in certain circumstances, such as those where humans would have difficulty reproducing with genetically estranged individuals, they would not avoid incest when having offspring. Although it should be noted that, in the human experiments included in the study, only the mating preferences of the study subject were compared, with computer-generated images that looked more like himself, compared to less similar images.
In conclusion, Regina Vega-Trejo argues that “our findings highlight the need to rethink the widely held view that inbreeding avoidance is a fact, at least with respect to experimental studies.”
References:
de Boer, RA, Vega-Trejo, R., Kotrschal, A., & Fitzpatrick, JL (2021). Meta-analytic evidence that animals rarely avoid inbreeding. Nature Ecology & Evolution. Published. https://doi.org/10.1038/s41559-021-01453-9
