March 23, 2004
Closely Related Mountain Gorilla Males Less Likely To Fight

Mountain gorillas get along better across social groups when they are more closely related.

Scientists studying the elusive western gorilla observed that neighboring social groups have surprisingly peaceful interactions, in contrast to the aggressive male behavior well documented in mountain gorillas. By analyzing the DNA from fecal and hair samples of the western gorilla, scientists uncovered evidence that these neighboring social groups are often led by genetically related males. These findings suggest connections between genetic relationships and group interactions, parallels with human social and behavioral structures, and clues to the social world of early humans.

In the new work, reported by Brenda Bradley and colleagues at the Max Planck Institute for Evolutionary Anthropology and Stony Brook University, the researchers collected DNA samples to characterize patterns of paternity within and among western gorilla social groups. The authors found that a strong majority of silverbacks were related to other silverbacks in the area and that in almost all cases, the nest sites of related silverbacks were found near each other. It was already known that both male and female western gorillas leave their natal group once mature, but the new findings suggest that the dispersing males may remain in the vicinity of male kin, forming a so-called "dispersed male network."

It makes sense that selective pressures would favor a greater willingness to harm those more genetically distant. Closer relations share more DNA in common and therefore their well-being and reproductive success is more in the interest of their close relatives than is the case with more distant members of the same species.

The researchers theorize that the dispersed male network and the social behavior of the western gorilla may be connected, in part because peaceful interactions between related males may be beneficial. This idea is in keeping with kin-selection theory, a well-regarded set of ideas for how related members of a society interact to benefit the related group. According to the authors, western gorilla male networks may benefit younger males as they attempt to attract females and form new groups, since male-male aggression is thought to hinder the acquisition and retention of females. Similar scenarios have been reported for some bird species, and there is ample evidence of such relationships underlying aspects of human social interactions, including marriage patterns. In addition, some relevant aspects of western gorilla society are shared with chimpanzees. The new findings point to characteristics that appear to be held in common between humans and some other African apes, suggesting that kinship patterns both within and among groups may have played an important role in shaping the social world of early humans.

I'll bet that humans will eventually be found to have genetic variations that encourage this sort difference in behavior as well.

Share |      Randall Parker, 2004 March 23 10:02 AM  Trends, Human Evolution

Stefan Jones said at March 25, 2004 4:30 PM:

"I'll bet that humans will eventually be found to have genetic variations that encourage this sort difference in behavior as well."

Probably a safe bet. But I hope we don't find this out soon, because we're not ready to deal with stuff like that.

Although, the only way we may have to learn to deal with stuff like that is to deal with stuff like that, so we're probably in for another round of civil rights struggles.

And bitter marital disputes over stuff like: Whether a developing fetus should have the gene for the Macho Dickhead behavior trait suppressed. ("I'm a macho dickhead, and my pappy was a macho dickhead, and no son of mine is going to be sensitive and tolerant!")

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