Neither demographic interviews nor the past 7 years of working with the Tsimane has turned up many overt cases of people dying from heart attacks, Gurven said. The Tsimane data tell us that inflammation alone may not be destructive in terms of its effects on long-term health. However, that might only be true in the context of an active lifestyle, lean diet, and possibly (and this part is more controversial) with a history of parasitism.

The researchers note that the Tsimane may have a distinct genetic expression compared to people in developed countries. Specifically, there is overexpression of the human leukocyte antigen, which has been linked in cell studies to plaque erosion.

We observed low levels of atherosclerosis and associated cardiovascular disease among Tsimane, suggesting that these conditions may have been rare throughout pre-industrial human history, Crimmins said. We may not be built for the world we live in. The Tsimane are perhaps a better model for the world we are built for.

We don ™t know for sure that as younger people today get older that [arterial disease] won ™t increase, Gurven said. More heart disease may be on the horizon if lifestyles change rapidly.

Jung Ki Kim and Caleb Finch of the USC Davis School of Gerontology and the Andrus Gerontology Center at USC and Hillard Kaplan of the University of New Mexico also contributed to the study.

Gurven, et al., Inflammation and infection do not promote arterial aging and cardiovascular disease risk factors among lean horticulturists, PLoS ONE 4(8): e6590.

dx.plos/10.1371/journal.pone.0006590.