Essence of human

Fascinating book review on the NYT (HT: Mockingbird blog) talking about the neurological roots of de-humanization, from genocide to slavery. In the book Less Than Human, philosopher David Livingstone Smith argues that we may be in some sense hard-wired to de-humanize people:

Smith clearly explains why many cognitive scientists believe this tendency is innate and then links it to another predisposition that seems “built in” to the human mind: our inclination to see living things in hierarchies, as in the “great chain of being” of medieval European Christians, with God at its perfect top, human beings above “higher” animals, and so on down to worms and plants. Because we feel that living things are defined by their essence, and because we feel that each creature has its rank in the world, Smith argues, dehumanization comes easily to the human mind: we accept that someone can look human but have a sub­human essence, and we accept that what is not human must be inferior. “When we dehumanize people,” he writes, “we think of them as counterfeit human beings.”

But reviewer David Berreby thinks this explanation doesn't match reality:

All these troubles arise because Smith’s insistence on immutable essences is only half right: people do categorize themselves and others using essences, but there’s nothing immutable about them. If, like trained philosophers, we could settle for good who is essentially human and who is a zombie vampire squid, we wouldn’t have, or need, this drama of dehumanization, rehumanization, then more dehumanization, and so on. Instead, the who-is-and-isn’t-human question is never truly settled. In fact, it is the dynamic, even mercurial nature of “real human” status that makes this mystery of our psychology so fascinating. What Amenemhet wants us to remember isn’t that he thought Asiatics were dogs, but that he made them act like dogs.

It's something worth thinking about: given dynamic conceptual frameworks, how do we become more just? Is it by taking the philosopher's approach, which is essentially to make our concepts more static, or is there a way to account for justice for an evolving human consciousness?