The Israeli invasion of Gaza, and the preceeding months of rocket bombardment from Gaza by Hamas militants, bring to mind once again to dismaying human tendency to dehumanize those different from ourselves. Of course, this is hardly a new trait. To the contrary, one might suspect that it goes back to the dawn of the human race, and perhaps even before. A good argument can be made that this trait is genetically ingrained, having been selected for over millenia as a trait that promoted the survival of human populations.
If one considers the situation of primitive humans, they would have existed as small bands of hunter/gatherers. The bands would generally have consisted of genetically related individuals, similar to how other simians such as chimpanzees exist now. Such a group would have needed a territory within which to hunt and gather. As with other territorial species, what goes along with having a territory is defending it from competitors — in this case, other bands of humans. That defense would presumably involve, at least at some points, combat with the competing bands.
As humans developed intelligence, it could have become potentially problematic to be fighting other humans. After all, as has been pointed out, altruism is evolutionarily advantageous to a group. Altruism says that one helps out others like oneself — more specifically, in ones own tribe or group. Yet here were humans having to, on the one hand, help each other, and, on the other, fight with each other. The solution was to see those not in one’s group as being “not human”. Going along with this would be development of distinctive clothing, markings, insignia, etc. that would identify members of the same group to each other. Those with the same markings/clothing/insignia were fellow humans to be helped; those without, non-human competitors to be at best ignored and at worst attacked and routed and/or killed.
It is not at all hard to see how these two traits — using common identifiers among members of one’s own group and dehumanization of those in other groups have been maintained over time. While there’s no question that there is some amount of evolutionary detriment when tribes kill one anothers’ members, the benefit to the triumphant tribe in more and better territory probably more often than not transcended its losses through warfare. Indeed, as civilization developed, warfare took on additional characteristics — such as the capture of one’s opponents as slaves — that increased the benefit to the winning side. I’m not saying that these latter traits are genetic. Once civilzation took hold, I would think cultural inheritance became far more powerful than genetic inheritance in promoting the continued evolution of societies.
Nevertheless, it seems that the trait of dehumanizing those different from one’s own group has remained beneficial over much of human prehistory and history. Only within the very recent past, as humans of different types have found themselves living closer together and having to cooperate in human societies, has it become evident that the dehumanization of those different than oneself has a large downside.
It would be nice to think that humans, as intelligent beings, could realize that the dehumanization of those different from oneself was no longer useful, and indeed counterproductive, and get beyond it. However, humans are animals, and the genetic traits developed over tens of thousands of years are not easily dismissed. That is not, however, to say that humanity is stuck with forever fighting among subgroups, be they racial, ethnic, religious, or cultural. There have been notable examples of where people from differing groups have been able to recognize their common humanity and develop a broader cohesion. Indeed, some entities, such as the Catholic Church and the United States, have developed in large part by amalgamating a whole range of different groups of people into a much larger and broader group. However, the basic dehumanizing tendency remains; it just get directed against those not yet in the large group.
More basically, it seems to me that if we are ever to get beyond the human tendency to dehumanize and attack other who are “not like” ourselves, we need to acknowledge this potentially genetic trait and figure out ways of getting around it. Just as humans have developed clothes to replace the fur we no longer have, and just as we have developed therapies to offset various genetic deficiencies carried within the human genome, perhaps we can devise therapies to be administered during childhood to offset the human tendency to dehumanize other humans. If not, the increasing density of human populations will assure that conflict will only escalate exponentially with the growth in population.