Dump nature/nurture

 Why do we always blame either nature or nurture for what we do?

My genes made me do it.  My upbringing made me do it.  My culture made me do it.  My biology made me do it. No matter what “it” is, we always seem to want to have one real reason for why we do it—and that “real” reason seems to fall into two camps: nature or nurture.   

This pattern of pitting biology and evolution versus culture and life experience is a giant mistake. The two realms are not separate from one another and the dichotomy keeps us from getting at better, albeit more complex, answers about why we do what we do.

Human behavior is “naturenurtural.” It is a synthesis and fusion of nature and nurture, not just the product of adding nurture to nature. There are not two halves to being human. When we think about humans, it’s a mistake to think that our biology exists without our cultural experience and that our cultural selves are not constantly entangled with our biology. Simple examples of this kind of engagement can be found in things like our adult height (a product of the integration of at least genes, nutrition/diet, physical activity, climate, early life social experience, and conditions of health and disease) or the ability to throw a baseball and kick a soccer ball (which can be influenced by integration of at least health, height, training, structure of lower limb muscles, altitude, nationality, sex, gender, peer group, and diet). Humans are neither a blank slate nor are they preordained entities; both of those perspectives miss the boat: we are naturenurtural.

But a concept like “naturenurtural” rarely springs to mind when we see something impactful, dangerous, “sexy,” or otherwise attention getting (such as war, domestic abuse, terrorism, rape, etc…).  In these cases we have a tendency to try and explain “it” by stating that it is part of our nature, an "evolved tendency" or that it is due to our nurture, the product of a specific social or environmental history. This approach is doomed to failure as it gives us an incomplete answer at best and the wrong answer at worst.

A great example of this very human tendency can be found in our interest in the behavior of another species: the chimpanzee. In particular we are fascinated by the fact that chimpanzees can be really violent and sometimes even kill each other.  Not surprisingly, debate about this behavior has been framed in the classic “it’s nature or nurture” context… In the case of the chimpanzees, it’s generally considered an evolved strategy of violence, or a by-product of human encroachment and disturbance of chimpanzee habitat.

A recent publication in Nature outlines the data from 152 Chimpanzee-on-Chimpanzee killings at 22 sites (58 observed, 41 inferred, and 53 suspected killings) over the last 50 years (or so). The study asserts that this is an important issue for chimpanzees (which it obviously is), but also for humans as we try to understand why lethal violence like this could occur in another complex social species (and one that is our close evolutionary cousin). This is also part of a debate about humans…Is a tendency to lethal violence natural or nurtural?  And if chimpanzees do it then maybe it’s part of our natural heritage as well.

The article frames the debate about why chimpanzees kill via two opposing explanations: a) lethal violence is the result of adaptive strategies, such that killers ultimately gain fitness benefits by increasing their access to resources such as food or mates (nature), or b) lethal violence is a non-adaptive result of human impacts, such as habitat change or food provisioning (nurture).

The killing events include lethal violence within groups and between groups; lethal violence by males, by females, and by both; and lethal violence directed towards males, towards females, towards adults and toward infants, weaned and unweaned.  The patterns vary dramatically between locations and times as well.  

There’s no debate that chimpanzees sometimes kill other chimpanzees, but there is a lot of variation in how, when, and where this happens, and thus, it’s not unreasonable to think that there might be a range of explanations as to why it happens (see here for summary and links). 

But that’s not how the data are presented, nor how the answers are framed in the article.  The authors of the study simply lump everything together and assert that all of this is best explained either by an adaptive pattern or by human disturbance.  They come out on the side of adaptive pattern. 

But does this artificially limited choice and the resultant answer actually get us anywhere?

So much variation in events, participants, contexts and outcomes, of this very complicated suite of behavior in this amazingly complex primate--and we are supposed to be content with a “their genes made them do it” vs. “their environment made them do it” comparison?  We mustn’t buy it.  Not for chimpanzees and not for ourselves.  So what if this is complicated, messy, and difficult to understand? So is life – deal with it. No one said it would be easy, so no one should be satisfied with such simple explanations.

Chimpanzee lethal aggression is a fascinating and complex reality and to expect a single and simple explanation for it is to ignore (as we often do) what we really know about the untidy reality of the world. To be fair, many folks who work with Chimpanzees, violence and warfare have pointed out the complexities involved here and do not support simple dichotomies (see here for example). Even some of the study’s authors, like Jill Preutz, have made serious efforts to highlight the complexity involved.

I sidestepped using a direct human example here to make a point: if other species are so darn complicated that explaining their behavior can’t be simply assigned to nature or nurture, then there is no way that we should do it for humans. Life is complex, whether one is human or a chimpanzee...  And simple explanations for seriously complicated realities are woefully insufficient.  

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