Saturday, February 13, 2010

The genetic roots of war?

The problem with the theory of evolution is not that it is wrong, but that so many people use it to construct pseudo-scientific stories. The typical story begins with a factual observation of trait X or behavior Y. How did it arise? It must have had evolutionary origins (and the hidden postulate here is that this trait or behavior must be genetically determined). Since we observe this X or Y, and we've said it has arisen from evolution, it must have been acted upon by natural selection, so yet another story is made up about how it provides a competitive advantage to the organism that possesses it. The hard work of science, the establishment of a causal chain, is ignored. The problem is compounded in the study of the more complicated animals, like apes, that can possibly have culture.

As a simple case in point
: "Killer chimps fuel debate on how war began".

Observation: "...a growing number of documented incidents of chimpanzees ganging up on, hunting down and killing each other"

Jargonification: "“Lethal coalitionary aggression is part of the natural behavioral repertoire of chimpanzees,” writes David Watts of Yale University in New Haven, Connecticut.

Story-making: "Watts declares the incidents back up a proposal that war is rooted in evolution. This view, called the imbalance of power hypothesis, holds that animals that conduct mutual group violence do so because it helps them win resources and territory. This in turn lets them survive longer and breed more—and all living species, evolutionary theory holds, descend from those that were able best do those things in the past.

The imbalance of power hypothesis states, in other words, that evolution favored humans and chimps who warred when and because they could get away with it. “This makes grisly sense in terms of natural selection,” said Richard Wrangham, a professor of anthropology at Harvard University in Cambridge, Mass., and the author of the hypothesis."

--- Notice what is missing here. To constitute a scientific explanation, we'd have to find the genes that govern this behavior - i.e., show how a gene or genes acting in concert cause human or chimpanzee "lethal coalitionary aggression". And we have to rule out that this is learned behavior that is transmitted from generation to generation. Then, there are several different ape behaviorial repertoires - e.g., chimpanzees are aggressive, but bonobos are not (if I understand correctly); and to understand the roots of human warfare we'd have to know which ape we descended from and whether the natural selection pressures that humans encountered during their evolution accentuated or diminished the various traits of the parent ape.

Personally, I've always wondered how a chimpanzee baby brought up by bonobos would behave. It shouldn't be a hard experiment to perform.

Anyway, I woke this morning to NPR's Radiolab where I heard of Robert Sapolsky's "A Natural History of Peace" in Foreign Affairs magazine. Since that is hidden behind a paywall, here are the essential findings from a NYT article from 2004:

No Time for Bullies: Baboons Retool Their Culture
Published: April 13, 2004

Among a troop of savanna baboons in Kenya, a terrible outbreak of tuberculosis 20 years ago selectively killed off the biggest, nastiest and most despotic males, setting the stage for a social and behavioral transformation unlike any seen in this notoriously truculent primate.

In a study appearing today in the journal PloS Biology (online at, researchers describe the drastic temperamental and tonal shift that occurred in a troop of 62 baboons when its most belligerent members vanished from the scene. The victims were all dominant adult males that had been strong and snarly enough to fight with a neighboring baboon troop over the spoils at a tourist lodge garbage dump, and were exposed there to meat tainted with bovine tuberculosis, which soon killed them. Left behind in the troop, designated the Forest Troop, were the 50 percent of males that had been too subordinate to try dump brawling, as well as all the females and their young. With that change in demographics came a cultural swing toward pacifism, a relaxing of the usually parlous baboon hierarchy, and a willingness to use affection and mutual grooming rather than threats, swipes and bites to foster a patriotic spirit.

Remarkably, the Forest Troop has maintained its genial style over two decades, even though the male survivors of the epidemic have since died or disappeared and been replaced by males from the outside. (As is the case for most primates, baboon females spend their lives in their natal home, while the males leave at puberty to seek their fortunes elsewhere.) The persistence of communal comity suggests that the resident baboons must somehow be instructing the immigrants in the unusual customs of the tribe.

Uust one case like the above is a reminder that anyone who wants to find the genetic origin of human or ape behavior has to first have to rule out learned behavior, or else actually find the causal chain of gene -> physiology -> behavior before feeding us stories of evolution.

PS: from the NYT article:
The report also offers real-world proof of a principle first demonstrated in captive populations of monkeys: that with the right upbringing, diplomacy is infectious. Dr. Frans B. M. de Waal, the director of the Living Links Center at the Yerkes National Primate Research Center of Emory University in Atlanta, has shown that if the normally pugilistic rhesus monkeys are reared with the more conciliatory stumptailed monkeys, the rhesus monkeys learn the value of tolerance, peacemaking and mutual hip-hugging.

PPS: Summary of Sapolsky's Foreign Affairs article:

Humans like to think that they are unique, but the study of other primates has called into question the exceptionalism of our species. So what does primatology have to say about war and peace? Contrary to what was believed just a few decades ago, humans are not "killer apes" destined for violent conflict, but can make their own history.