The Scientific Study of Human Nature

I'm sure that the scientific study of human nature is being undertaken in various research universities and laboratories all over the world.  But take a look at the scientifically literate (but not formal science) writings, I think they are decidedly unscientific.

Let's look at a couple of articles.   First,

Male chimps and humans are genetically violent---NOT! 

Is violence in our genes?

Published on March 29, 2011 by Darcia Narvaez, Ph.D. 

Narvaez asks:

Do chimpanzees in the wild want to kill others? Is murder common among wild chimpanzees? Do male chimps (and their cousin male humans) have "killer" "demonic" instincts towards their fellows? If you look at the data, the answer to these questions is a resounding NO! But these beliefs are "gospel" in much of popular science. This misinformation colors our view of humans and human nature. What are the ramifications?

Since there is a lot of potential distraction here, let me say, for this essay, it is irrelevant whether chimpanzees in the wild want to kill other, whether murder is common among wild chimpanzees and whether male chimps have "killer" "demonic" instincts towards their fellows.  The key question is whether the behavior of male chimpanzees can tell us anything about "their cousin male humans".

The common narrative among the scientifically literate is, of course it does.  Narvaez spells it out:

If you believe that chimpanzees are naturally violent and murder their fellow chimps, then you can easily extrapolate to humans. You have evolutionary evidence for the belief that it is natural for humans do the same thing.

Second,
Is Lethal Violence an Integral Part of Chimpanzee Society?
Like it or not, some chimps are violent.
Published on April 14, 2011 by Kevin D. Hunt, Ph.D

Most of the essay is about what is irrelevant here, whether chimpanzees are violent or not.  It is the conclusion, that studying chimpanzees tells us something about humans, that is interesting (emphasis added).

I agree with Dr. Narvaez when she writes: "We have ourselves to blame, not selfish genes, not evolution... We can change the practices and beliefs" to become nonviolent. Many researchers who have documented violence among primates would also agree with her. Certainly Wrangham agrees with her on this point. In Demonic Males, Wrangham and Peterson wrote: "We are blessed with an intelligence that can...draw us away" from violence, from a demonic evolutionary history.

A simple scientific problem with the assumption that chimpanzee behavior can tell us something about humans is that the explanatory chain - the causal links are weak.   The claim is not just that behavior is genetically determined, but that the common ancestor of modern-day chimpanzees and modern humans bequeathed both species genes that drive murderous male behavior.

The Bonobo, Pan paniscus, is another extant great ape closely related to the chimpanzee, Pan troglodytes

Nature :

The bonobo genome compared with the chimpanzee and human genomes
doi:10.1038/nature11128
The Bonobo, Pan paniscus, is the other extant great ape along with the chimpanzee, Pan troglodytes

This paper assumes that behavior is genetically determined (though no one has conducted the very feasible experiment of bringing up chimpanzee infants in a bonobo society or vice versa.  Given that we're driving these animals to the verge of extinction, it seems unlikely that such an experiment will ever be conducted.  Also, we do not know whether it is only modern pressure on the chimpanzees' environment which leads to murder being a successful strategy, assuming that male chimpanzees are indeed murderous, e.g., latent violence might have turned into actual violence recently.)  Let's not take issue with these assumptions then, and proceed.

The authors of the Nature paper tell us:

Bonobos and chimpanzees are highly similar to each other in many respects. However, the behaviour of the two species differs in important ways. For example, male chimpanzees use aggression to compete for dominance rank and obtain sex, and they cooperate to defend their home range and attack other groups. By contrast, bonobo males are commonly subordinate to females and do not compete intensely for dominance rank. They do not form alliances with one another and there is no evidence of lethal aggression between groups. Compared with chimpanzees, bonobos are playful throughout their lives and show intense sexual behaviour that serves non-conceptive functions and often involves same-sex partners. Thus, chimpanzees and bonobos each possess certain characteristics that are more similar to human traits than they are to one another’s. No parsimonious reconstruction of the social structure and behavioural patterns of the common ancestor of humans, chimpanzees and bonobos is therefore possible. That ancestor may in fact have possessed a mosaic of features, including those now seen in bonobo, chimpanzee and human.

 Therefore, the evolutionary relationships of bonobos, chimpanzees and humans is worthy of study.  The genetic analysis reveals, first the evolutionary relationship (figure 3b)

The arrows with the numbers (45,000; 27,000; 12,000) are estimated "effective population sizes".   The main points of the diagram are that humans (H), chimpanzees (C), and bonobos (B) had their last common ancestor some 4.5 million years ago.  Bonobos and chimpanzees had their last common ancestor 1 million years ago.

The answer to

We are blessed with an intelligence that can...draw us away" from violence, from a demonic evolutionary history

is that bonobos and chimpanzees share much more of a common "demonic evolutionary history" than they do with humans, and yet are so different, so the alleged "demonic evolutionary history" has not been shown to be relevant.


Second, the genetic sharing among the three species (figure 3a):

H,C,B share 95% of their genome.  In 1.8%, B and C are closer to each other than to H, in 1.6% H and B are closer to each other than to C, and in 1.7% H and C are closer to each other than to B.
 

To truly explain murder in the evolutionary/genetic paradigm we would have to, at a minimum:

1. Explain how the common ancestor of bonobos and chimpanzees could diverge to such different modern observed social characteristics regarding murder one million years ago.

Either the evolutionary pressures were different, or else some chance circumstance led to two different stable equilibriums.

2. Trace behavior differences to the 1.6% and 1.7% where B is closer to H and C is closer to H.

3. (Assuming it is in the genes) show that the violent-C part of H overrides the B-part of H, and is indeed the cause of H's homicidal behaviors (instead of homicide being a learned behavior, given the plasticity of H's brain, you can't rule that out with an "obviously....").

4. Answer why both the B- and C- social equilibria are not both available to H.  (Please see this about baboons.)

Until these are done, we humans are as much bonobo as we are chimpanzee, and if indeed bonobos and chimpanzees differ in their behaviors for innate causes, we really have little clue as to which one determines human behavior.  (Please let's not get into the fallacy of "humans murder, so obviously it is the chimpanzee side that predominates", where one is mixing up the fact to be explained with the explanation.)

While evolution and genetics are valid, nevertheless the public consumption of them is like that of the Biblical God.  The public is convinced that everything is a result of God's Will, though God's Will is for the most part unknown.  In a similar way, the public swallows just-so stories about humans and draws implications from them (even though some of the story should be knowable). As Narvaez wrote:

Sociobiological or evolutionary psychology theory, popular among most science writers, can mislead, telling us "just so" stories that fit current cultural norms and treating them as facts (Hart & Sussman, 2009).