For humans, incest is a social taboo backed by sound biological reasoning. Mixing of genes is beneficial as it increases genetic diversity, while offspring between direct relatives often produce genetic defects. However, according to recent research published in Nature Ecology and Evolution , many animals do not make distinctions when choosing a mate.
This may seem surprising, yet numerous theorists have pointed out for decades that inbreeding is not always bad. In fact, when the choice of partner is limited, it could even be beneficial.
How do animals choose their mate?
Animals take into account various factors when choosing a mate. One of them is their degree of kinship, but animals are also interested in the resources that the couple can provide (such as food) and if they carry desirable genes.
Choosing a non-related partner is attractive as it increases the genetic diversity of the offspring. Mating with a relative, on the other hand, increases the likelihood that parents will pass on rare genetic diseases to their offspring.
So why do some animals practice incest? An obvious scenario in which animals mate with their relatives is when there is simply no other option. If animals are to pass on their genes, it is to be expected that they would rather have offspring with a relative than not reproduce at all.
However, there is a completely different theory behind inbreeding in some animals. According to Richard Dawkins, an evolutionary biologist, there is the so-called ‘selfish gene’. That is, some animals want to pass on as many genes as possible. Thus, from this perspective, the more genes an animal passes on to the next generation, the better it will do.
On the other hand, animals that avoid inbreeding also have to expend energy looking for a mate, even as they learn to distinguish relatives from individuals with whom they are not related. Saving energy is sometimes crucial for the survival of animals and, by extension, the survival of their genes. For this reason, learning to avoid inbreeding may not always be the best strategy for some animals, especially if they are in danger of extinction.
