Contrary to widespread belief among biologists, according to authors of a recent wide-ranging study:
Biologists have long believed that it’s adaptive for most species to avoid mate pairings between close kin because of the potential genetic fallout, but a meta-analysis published May 3 in Nature Ecology & Evolution challenges this long-held assumption…
The finding also bolsters what were previously considered to be unexpected findings of frequent inbreeding or a lack of inbreeding avoidance in some wild populations.
The authors examined nearly 140 experimental studies of inbreeding avoidance conducted on 88 species—everything from fruit flies to humans—and found little evidence that animals on the whole prefer non-relatives.Christie Wilcox, “Incest Isn’t Taboo in Nature: Study” at The Scientist
The paper is open access, via a SharedIt token.
Thing is, it was never clear exactly what the mechanism is supposed to be for animals to try to avoid mating with kin. So it’s no surprise that most aren’t really doing that anyway.
Maybe if researchers focus on situations where breeding with close kin can really be shown to be happening, they can identify how the animals know. Then try to find out how such mechanisms would come to exist.
One problem with Darwinian thinking is that theory comes first and then evidence is found for it. That seems to have happened with beliefs about animals avoiding mating with kin.
Even author Regina Vega-Trejo falls into that trap when discussing the comparatively smaller number of animal species that prefer to mate with kin:
One of the things to keep in mind is that when you make a decision to mate or to reproduce, what you basically want is to pass on your genes. And half of your genetic material will go to your offspring, but the other half of the genetic material will come from your partner. And if you mate with your brother, for example, you’re actually passing on more genes that belong to you [because he has some of the same genes]. So, that might be one of the things that animals—I mean, they don’t think or consider—but that’s one of the advantages [of inbreeding].Christie Wilcox, “Incest Isn’t Taboo in Nature: Study” at The Scientist
No, indeed. The animals don’t “think or consider.” They also don’t want to pass on their genes. That’s ultra-Darwinian nonsense. They want to mate and whatever happens is what happens. Darwinian nonsense around a drive to pass on genes simply clouds the picture.
See also: Mice from opposite coasts of North America show the same changes in genes. The house mouse, beloved of cats, only arrived in North America with Europeans, so there aren’t millions of years to make up a story about how things happened.