Do you believe in human nature?

My professional field of study is gene-environment interactions, or what philosophers and social scientists call nature vs. nurture. That is why, whenever I’m asked if I believe there is such a thing as “human nature” my answer is yes and no. Yes, in the sense that the genetic makeup of the human species is distinct enough from that of other species to make us different in a variety of non-trivial respects (of which having developed blog technology is just one). No, because human beings are genetically contiguous with other primates (which means there are very few things that are truly uniquely human), and also because we know that genotypes can produce very different outcomes depending on what the environmental conditions are (a phenomenon known in biology as phenotypic plasticity).

And yet, it is amazing how polarizing this sort of question can be, and has historically been. Moreover, it is interesting to find predictable (though not absolute) differences between practitioners in different fields. A philosopher colleague of mine, for instance, was recently incredulous that I would even mention the term “human nature” in a class we were teaching jointly. For her, it was simply laughable that any sensible person would entertain such a clearly silly notion. Surely, her argument went, decades of cultural anthropological studies have shown that human behaviors are pliable at will, that there are no human universals, and therefore no “human nature.”

Au contraire. It is quite obvious that there are limits to the range of both human physical and behavioral attributes. Going to the gym and eating less will make you lose weight, but it will not get you six-pack abs unless you are genetically predisposed to have them (in which case, you’ll get them even if you don’t go to the gym and eat cheeseburger for breakfast). It’s unfair, but so is life. Analogously, most of us can learn to play a musical instrument by practicing, but -- contrary to the famous quip -- it takes a lot more than practice to get to Carnegie Hall. As for human universals, there are quite a few, some of which we actually share with other animals, such as the fight-or-flight response, or the expression of many of our emotions, as elegantly documented already by Darwin.

On the other hand, I get equally annoyed when I hear some of my colleagues (Steven Pinker comes to mind) going on and on about how we are not a “tabula rasa” because our genes encode much of what we are and do. Once again: genes encode proteins, and absolutely nothing else. From proteins to complex traits such as cognitive ones there is a vast unknown ocean referred to as “epigenetics” (literally, beyond genetics), the surface of which we are barely beginning to scratch. Our genetic makeup certainly poses limits to what we can and cannot do, but how ample those limits are is currently largely beyond the scope of human biology, partly because we cannot do the right experiments that would settle the matter (it is both impractical and unethical to breed human beings and raise them under controlled environmental conditions, which is what we do with other animals and with plants when we wish to study gene-environment interactions).

Even among philosophers, of course, the question has hardly been settled. While John Lock orginated the phrase tabula rasa, Aristotle famously thought that the essence (the nature, we would say) of humanity consists in our ability to reason. Judging from the history of the intervening 23 centuries, he probably overestimated how sapiens we really are. Nonetheless, humans are the only species with a developed language, art, science and technology. And surely those things ought to count as evidence of the existence of a human nature. The problem with trying to be a reasonable skeptic is that one easily makes enemies on both fronts of any debate: you acknowledge that genetics does set limits to human characteristics, and you get accused of being a genetic determinist and possibly encouraging eugenics. You grant that the environment plays a sometimes major role and you are ridiculed as an anti-scientific fuzzy thinker. Wake up, ladies and gentlemen on both fronts: the reality is both more complex and more fascinating than either caricature would allow. It is neither nature nor nurture, it is -- as the title of an unusually balanced book by Matt Ridley puts it -- nature via nurture.