The conquest of sociality in natural evolution

One of the most fascinating mechanisms showing how behavior can influence the selection of specific genetic traits and therefore the Darwinian evolution of a population is the one underlying the theory of self-domestication. In short, self-domestication is a hypothesis that states that social living beings tend to select for pro-social traits in their own kind, which is why the genetic components underlying these traits end up being enriched in the species, favoring the prevalence of specific genotypes over time. Up to now, clear evidence of this process had been found in humans and bonobos, but it was unclear whether mechanisms of this type could have taken hold also in very different species, and particularly outside primates.

In a recently published work, a group of biologists and linguists has found evidence suggesting that wild African elephants may have domesticated themselves too. Interest in elephants arose when the team compiled a list of 20 characteristics they identified as the result of domestication, either by themselves or led by humans. When comparing humans, bonobos and wild African elephants, some similarities are found in some of those traits. All three species, for example, have evolved play behavior; they are all sociable and have long childhoods. All three also have a remarkable development of parental care and tend to show attachment to all members of the group to which they belong. Furthermore, from a physical point of view, they all have shorter jaws than the species from which they derive.

To obtain proof that was not only circumstantial of their hypothesis, the researchers therefore selected a series of genetic traits that appear to be shared by many species subjected to the domestication process, and then used humans and bonobos as a filter to identify among these traits those potentially linked to the phenomenon of self-domestication. The corresponding genetic variants were then looked for in wild elephants, leading to the identification of at least 79 genetic traits associated with domestication found in wild African elephants. This is a much higher number of genetic traits than it would be reasonable to expect on the basis of pure chance, and, since these are genes whose association with behavioral and physical traits useful for domestication is very well understood, it appears evident that the hypothesis of a self-domestication process which also occurred in elephants, in parallel to what was observed in primates, is at this point well founded. Furthermore, since the most recent common ancestor of humans and elephants is probably the most recent common ancestor of all placental mammals, the newly published finding has important implications for the convergent evolution of domestication traits in all mammals; if this element were to be confirmed, the typical traits of pro-sociality due to self-domestication are potentially traceable in most modern mammalsexcept for those cases in which they have been selectively subjected to negative selection for disparate reasons (and difficult to hypothesize at first).

That is, mammals would be genetically predisposed to the development of genetic variants useful for group life, and these same variants would then be usable for their domestication; in the right conditions, therefore, the domestication process that man has carried out on a large number of very disparate species (and in very different human cultures) would therefore be a phenomenon favored by the widespread presence of some selectable gene variants, which they are spread in placental mammals from a very distant common ancestor. Self-domestication and prosociality would thus be part of the genetic potential of the group of vertebrates to which we belong; if this hypothesis is further confirmed, it follows that the corresponding traits have therefore been selected independently several times in the evolutionary history of this group, leading to evolutionary convergences that reflect the common original genetic substrate.