...the nature we share

ake, for example, the little round clumps of trees that dapple the savanna. Ecologists found that these clumps of trees are about the same size and shape as the thorn-fence corrals that herders use to pen up their animals and protect them from predators during the night. Inside the corrals, the animals drop their manure and tromp it into the ground, preparing the soil for the tree seeds that pass through their guts. When the herders have gone, the thorny corrals remain, protecting the circle of ground and giving the seedlings a head start.

"So what's really happening," Leslie says, "is that the animals are transporting nutrients from all over the landscape and depositing them in these corrals. And if you climb up to the top of a hill in Turkana, shortly after the rains, you can see circular patches of green that are the same diameter as these old corrals."

.: In the dry, harsh lands of Turkana, herds help maintain the social networks families need to survive the inevitable disaster. Photo by Paul Leslie; click to enlarge. :.

And Turkana people keep those big, scrawny herds for very good reasons. In their culture, animals represent the collective wealth, not only of individuals, but of families and groups. Borrowing and sharing are customary and expected, and marriages demand a transaction of as many as 75 large animals such as cattle and camels and perhaps 200 goats. These customs arose from an environment in which people "count on disaster," Leslie says. A Turkana family knows that drought, intertribal raiding, or livestock epidemics will almost inevitably wipe out some or all of the family's animals. A network of shared obligations reduces the risk of catastrophe for any one family, much as insurance does in Western industrial cultures.

"What people are maximizing is not productivity but the probability of persistence," Leslie says. "Under the circumstances, it wouldn't make sense for them to have fewer, fatter animals because people wouldn't be able to build those networks."

o are the hungry animals denuding the environment and spreading the desert? No, Leslie says. "What's controlling the populations of the animals is something that's extrinsic to the system itself, and that's rainfall. When there's a drought, and there's nothing for the animals to eat, their numbers get knocked down. Not all ecosystems are like that, but a lot of the dry lands of Africa are."

Some of the studies were "endlessly entertaining to the Turkana," Leslie says. Ecology students followed the camels around, weighing their dung, measuring the nutrients. Hydrologists studying water-percolation rates trucked water into the dry bush with a Land Rover, dug a series of holes, poured a measured amount of water into each, and then timed the water with a stopwatch until it disappeared.

"So the Turkana guys are watching all of this," Leslie recalls, "and they say, 'What's with this guy? How many times you gotta pour this water in there? I'll tell you what's gonna happen, it's gonna disappear.'"

.: African elephant. Photo by Paul Leslie; click to enlarge. :.

Leslie made a little more sense because he talked with people about things that were important to them — why they took their animals here instead of there, or why they had this mix of species in their herds rather than having more camels.

hile Leslie's team was studying the effects of people and their animals on the environment, they were also interested in how the environment affected the people. They measured growth and development in the children — height, weight, fatness, and immune-system function. They also studied fertility to learn how the environment might have been affecting the reproductive function of women and men.

"You assess that by measuring hormone levels at different times, and that entails taking urine samples and blood samples, which can seem a little odd to them," Leslie says. "If we hadn't already worked there for years, I never would have been able to get the blood samples from them. As it was, it took a lot of explaining to really make sure they didn't think we were doing some sort of witchcraft."

Studies in Turkana and elsewhere have challenged the notion that fertility is determined by social factors alone. Comparing nomadic and settled women, Leslie's team found significant differences in reproductive function, some of which appeared to be environmentally induced. "Among the most striking of our results is an extraodinarily high rate of pregnancy loss among settled Turkana women, but not among the nomads," Leslie says.

Work in this field, which is called reproductive ecology, is relatively new, Leslie says. And not all social scientists are comfortable with it, or with any other approach that would seem to imply that biology influences human behavior. In some universities, disputes over such questions have split anthropology departments apart, creating what Leslie regards as an unfortunate division between cultural and biological anthropologists.

.: Zebras in the Ngorongo crater of Tanzania. For hundreds or thousands of years, herders shared the savanna with wildlife. Photo by Paul Leslie; click to enlarge. :.

"Here (at Carolina) it is much, much better," Leslie says. "We have people who do work on both sides. Sometimes there are tensions, but we still like each other and go to the same parties, and we encourage our students to bridge those perspectives."

hese days, some of those students may wind up working with Leslie in Tanzania, but Turkana is off limits, for now. The area has become too dangerous, racked with ethnic and political violence. "Livestock raiders running around with spears is one thing," Leslie says, "but when they've got AK-47s, that's another."

That's a shame, Leslie says, because during his 15 years in Turkana, he made friends and earned the trust of the people he studied. He had also invested a big chunk of his life, learning the people and the landscape, and mastering the fine art of automotive repair in the bush. (He's spent untold hours under the working end of a Rover, his legs poking out in the sun.) Things are different in Tanzania, among the Maasai. The vehicles are more reliable. The land is richer, better watered. And the people do not range as far with their animals.

But in Tanzania, the issues are even more urgent than they were in Turkana. The Maasai and their way of life hang in the balance. Will they give up herding and settle for farming? Will their health decline as they grow more sedentary, more dependent on corn? Will their values and strong social networks decay?

"Tanzania is a wonderful place to work because it's spectacularly beautiful," Leslie says. "You drive to work through herds of elephants and zebras, and it's just gorgeous. But there are serious problems there, and in some ways it's very depressing to see what is happening to the people. They are bearing the entire burden of the conservation efforts. They are losing their livelihood. And it's all because they happen to be living where there are some pretty animals."

Leslie's research is funded primarily by the National Science Foundation, the Andrew W. Mellon Foundation, and the Rockefeller Foundation.

Neil Caudle is the editor of Endeavors magazine.
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