aggression

In the New Yorker, Jared Diamond writes a long article with an interesting personal account of revenge cycles in Highland New Guinea:

Hiring, supporting, and rewarding all those allies was a complex logistical operation. Daniel had to feed them during the actual days of combat, to arrange for houses in which they could sleep, and even, as he delicately phrased it, "to provide ladies for the warriors when they were homesick." Daniel estimated that, in the three years that it took him to get his revenge, he had to furnish about three hundred pigs. By custom, the pigs to be slaughtered during that long phase of preparation should be not one's own but, rather, stolen from the enemy clan. Yet Daniel had to be careful to steal only Ombal pigs and not to make the mistake of stealing pigs from other clans; otherwise, he would acquire new enemies.

Many students of anthropology may have seen videos of the large, showy, and ineffectual-seeming "public fights" between groups, and taken away the impression that such small-scale warfare could not be very dangerous. But in the context described by Diamond, this is only the surface of a deeper, more earnest pursuit:

Daniel emphasized the importance of distinguishing between long-range public fights and close-range private ones. He contemptuously described the former as a "small boys' game shoot." As he explained it to me, "Public battles are open not just to experienced fighters but also to new trainees, new allies hired to come and gain confidence, and fun-seekers. In a public battle, the fight-owners have the opportunity to see who really are the best marksmen, with the necessary experience to make quick but correct decisions." Such warriors are selected for the much more dangerous task of private fights, in which hired teams of stealth killers prepare ambushes. "That requires nerve, judgment, and presence of mind, to select the right target, and not to panic and shoot the first man who moves into a shootable position," he said. "Boys and young men are prone to make such mistakes and hence are excluded from the stealth parties."

At the outset of his essay, Diamond suggests that revenge cycles in small-scale societies are equivalents of the dehumanization induced by wars between states. I think this part of the essay is simplistic: he might have profitably explored the differences, the depth of which is suggested by the different psychological reactions that he mentions.

But the end, a personal account from a different culture, is much more evocative.

LiveScience reports on David Carrier's current paper in Evolution:

"The old argument was that [apes] retained short legs to help them climb trees that still were an important part of their habitat," said the study author David Carrier, a biologist at the University of Utah. "My argument is that they retained short legs because short legs helped them fight."

I won't be able to get the paper for awhile. The thesis is that short legs are adaptive to aggressive interactions because short, stout bodies are better for fighting. In addition to the primates mentioned in the article (of which there are only nine), Carrier has in previous papers (Pasi and Carrier 2003, Kemp et al. 2005) studied the relation of limb length and fighting ability among dog breeds.

It looks like Carrier is arguing that the biomechanical advantage of short legs in climbing doesn't really predict arboreality:

As indicators of aggression, Carrier looked at the weight difference between males and females and the male-female difference in length of canine teeth, which are used for biting during battle. Studies have shown greater aggression in primate species in which males tipped the scales relative to females.

Primates with the stoutest figures also ranked high on both aggression measurements. For instance, the gibbons boasted longer legs than other apes and also ranked low on the aggression scale. In contrast, male gorillas, which are more than double the size of females, were stout.

The lengthy legs didn't keep gibbons away from canopies either. "Gibbons are the best acrobats in the animal kingdom. There are no other animals that can move through the canopy the way a gibbon can," Carrier told LiveScience. "And they contrast male gorillas, which hardly ever climb. When they do climb they stay close to the trunk, they spend most of the time on the ground."

I don't know -- australopithecines don't have long canines, and their level of dimorphism has been subject to debate. So the comparison may not work. I'll have to see what the paper says.

References:

Pasi BM, Carrier DR. 2003. Functional trade-offs in the limb muscles of dogs selected for running vs. fighting. J Evol Biol 16:324-332.

Kemp TJ, Bachus KN, Nairn JA, Carrier DR. 2005. Functional trade-offs in the limb bones of dogs selected for running versus fighting. J Exp Biol 208:3475-3482.

Charles Siebert of the Times had a story this weekend about aggression by young bull elephants. It has a name now, HEC (human-elephant conflict). And it has taken a chilling turn:

Still, it is not only the increasing number of these incidents that is causing alarm but also the singular perversity -- for want of a less anthropocentric term -- of recent elephant aggression. Since the early 1990's, for example, young male elephants in Pilanesberg National Park and the Hluhluwe-Umfolozi Game Reserve in South Africa have been raping and killing rhinoceroses; this abnormal behavior, according to a 2001 study in the journal Pachyderm, has been reported in "a number of reserves" in the region. In July of last year, officials in Pilanesberg shot three young male elephants who were responsible for the killings of 63 rhinos, as well as attacks on people in safari vehicles. In Addo Elephant National Park, also in South Africa, up to 90 percent of male elephant deaths are now attributable to other male elephants, compared with a rate of 6 percent in more stable elephant communities.

Personally, I think that 6 percent is impressively high -- that is a huge toll in a species with such long life histories.

In human deaths:

In the Indian state Jharkhand near the western border of Bangladesh, 300 people were killed by elephants between 2000 and 2004. In the past 12 years, elephants have killed 605 people in Assam, a state in northeastern India, 239 of them since 2001; 265 elephants have died in that same period, the majority of them as a result of retaliation by angry villagers, who have used everything from poison-tipped arrows to laced food to exact their revenge. In Africa, reports of human-elephant conflicts appear almost daily, from Zambia to Tanzania, from Uganda to Sierra Leone, where 300 villagers evacuated their homes last year because of unprovoked elephant attacks.

It's a long story that goes into the study of elephant social behavior and relates psychological trauma in elephants to the mechanisms underlying it in humans. There's also a fascinating account of the time that a man-killing circus elephant was hanged (yes, hanged) for the crime.

UPDATE (10/10/2006): From Reuters:

Indians flee as elephants search for dead friend

RANCHI, India - Thousands of people in eastern India have fled their homes in fear as elephants crash through villages looking for one of their herd, which fell into a ditch and drowned over the weekend, officials said Tuesday.

Residents of Banta in Jharkhand state gave the 17-year-old female elephant a quiet burial three days ago, but 14 marauding elephants have been raiding the village ever since.

I find it eerily creepy the way that the journalists in these stories have chosen to anthropomorphize the elephants. Now, to be sure the elephant reactions may well involve a very similar psychological process to humans in similar situations (loss of companions, crowding in unfamiliar habitat). But here they are described in almost exactly the same terms that one would describe humans in the same situation (fighting off encroaching development, dealing with losses at the hands of other people):

With forest cover dwindling in eastern India, elephants and other animals regularly leave their forest homes in search of food, triggering conflict with locals.

The description of the rhino-raping is one of the few elements that really stand out as inhuman, and that's why it is so striking. But these stories have a very consistent theme, and it is a theme taken straight from Edgar Rice Burroughs. Somebody should teach these journalists better.