There is a strong prohibition against incest in modern societies, and biologists have long wondered why they knew it.
However, a review of “relative avoidance” studies in the case of animal mixtures argues that there is only one problem: the evidence is not here. Inbreeding can certainly have fatal consequences. We see it in everything from dogs to European aristocracy to hemophilia frequencies (up to the most frequent fatalities recently) from fighting to breathing. In both cases swimming in a very small gene pool increases the risk of ending up with two copies of harmful versions of a gene.
One desire to avoid animal reproduction has been used to explain the behavior of many animals, such as the way some animals move in the herd. It’s hard to imagine another explanation for the way the female band actually started a deadly battle between the mongooses packs so that they could go their way with the enemy in battle. Nevertheless, Dr. Rasa de Boer of the University of Stockholm argues that there is less evidence than is generally believed.
De Boer said in a statement, “People assume that animals should avoid mating with any relatives when given the chance.” “But evolutionary theory tells us that over a period of more than four decades, animals should be mated to relatives under a wide range of conditions, or even like animals.” De Boer has published an article in Nature Ecology and Evolution with three co-authors, reviewing 139 research papers on abstinence from sexual intercourse, either by Targaryen or Dollanganger. This included research into whether different animals, both captive and wild, avoid reproduction with their close relatives.
Although some studies actually avoided the issue of kinship, its impact was minimal across the entire sample. Furthermore, the authors argue, the scientists ’hatred of incest created a publication bias that would explain what little effect was found. “We call the study of the reproduction avoidance of living things the ‘elephant in the house’ and reject the notion that animals will avoid reproduction whenever possible,” de Boer said.
The authors claim that most animals show no reluctance to mate even with close relatives or even instant siblings. Even among humans we know that the prohibition of incest was not always as strong as it is today – the Pharaohs suffered the consequences of frequent marriages of their siblings, but still ruled Egypt for thousands of years. The authors conclude that paying for inbreeding may not be heavy enough to create a selective pressure in many animals that outweighs other aspects of the mate’s choice. The pressure to avoid relatives is probably weakest in animals where the population is large and sufficiently mixed that adults rarely encounter with relatives, or where opportunities for mating are rare.
