Lessons from the Tsimane
What can we learn about modern human health from a primitive tribe of people who live deep within Bolivia’s Amazon region? Plenty.
UCSB anthropologist Michael Gurven has discovered, for example, that heart attack and stroke–leading killers in modernsocieties–were probably rare throughout most of human history. They are almost unheard of among the Tsimane, a primitive tribe of hunter-gatherers in central Bolivia, despite high levels of a protein believed to cause heart disease in modern societies. In fact, the Tsimane’s lack of heart disease could be related to a very active immune system.
Tsimane typically have high levels of C-reactive protein, normally an indicator of atherosclerotic disease and stroke. They also suffer from significant internal parasites, which keeps the immune system just active enough to protect them from autoimmune diseases like rheumatoid arthritis, lupus, asthma and allergies, Gurven says.
What’s going on? Do parasites alter lipid metabolism and the immune system in ways that protect the heart? Is it diet? Vigorous physical activity? Genes? Less stress? These are all questions Gurven hopes to answer as his research goes forward.
Gurven has worked 10 years on the National Institutes of Health-funded Tsimane Health and Life History Project, which seeks to understand the impacts of ecology and evolution on the human life course. A collaborative project with Professor Hillard Kaplan, an anthropologist at the University of New Mexico, the study examines health, growth and development, aging, economics, and the biodemography of small-scale populations of hunter-gatherers and horticulturalists.
Humans share several unique features compared to other animals, among them that their children take a long time to mature and they have relatively big brains. These attributes would be impossible if not for very active cooperation among humans to acquire and share resources, Gurven says. For example, among hunter-gatherers, he says, children are expected to help, whether by collecting fruit or babysitting younger siblings. Even so, children don’t typically begin to produce more than they consume until they are in the late teens. This cost of development as the children grow could only occur if there’s a big boost in food production later in life, which requires an expansion of life span over time, Gurven says.
Gurven and his colleagues are particularly concerned with how life span evolves. Life expectancy in modern cultures has expanded, primarily through the elimination and/or reduction of infant mortality. End-of-life mortality also seems to be extending life span, Gurven says.
He wants to know: What is the optimal level of resources to maintain life?
“Each organism’s life history is a compromise,” he explains. “It’s costly to get nutritional food, costly to reproduce and costly to have strong immune defenses.”
With the Tsimane, researchers are studying their fertility, mortality and history, and their underlying physiology. They examine social behavior, economics, physical condition and health and try to tie it all together. There are more than 9,000 Tsimane, and they live in villages spread out over Amazonian Bolivia. Gurven’s project has recently expanded from 25 to 75 villages.
Gurven and his colleague Kaplan take turns traveling to Bolivia every few months, and Gurven spends most summers there. He also is in touch every day with his Bolivia-based team of staff, physicians and biochemists, who are trained to collect health care information.
Ultimately, the Tsimane Health and Life History Project may reveal much about the health of ancient societies, but is also shedding light on modern health quandaries.