(Photo courtesy of Ben Trumble and Michael Gurven)

A Tsimane man and his son fishing with bow and arrow.

On the second floor of Arizona State University's life science building, a massive refrigerator hummed as Professor Ben Trumble slid out a flat, stainless steel tray.

It’s one in an endless row of trays waiting to store test tubes filled with very rare blood samples from the healthiest hearts in the world.

“Each of these racks holds seven sets of 100,” said Trumble, who looks forward to filling the refrigerator to capacity. “We'll be able to store several thousand here.”

Trumble is an expert on parasites and pathogens and their impact on humans facing chronic diseases of aging. This summer he will guide students in his new lab on the Tempe campus.

Before he came to ASU, Trumble spent seven years with a team studying parasites and pathogens and their impact on the Tsimane people, an aboriginal tribe in the Bolivian jungle.

They found “Tsimane have the lowest level of atherosclerosis ever recorded.” To the point, Trumble said, “85 percent of Tsimane have no atherosclerosis at all, no coronary calcium.”

It’s the mirror opposite of most Americans, “85 percent of people in the U.S. in the same age range have atherosclerosis," he said.

Trumble’s colleague and director of the Tsimane project, Dr. Michael Gurven, began studying the tribe in 1999.“Ben is more a lab person, analyzing different biomarkers in the blood, whereas my background was more social behavior, cooperation, how people manage risk," Gurven said.

Such as the health risks the Tsimane face hunting and fishing for a daily meal versus the risk of relying on someone else to serve it through a drive through window.

The Tsimane people are the very rare few who live as man did 1,200 years ago, prior to the agricultural age. In the years since, Gurven said we’ve undergone an “epidemiological transition.”

“In other words, the shift from infectious disease to chronic disease," Gurven said.

By chronic, they mean diabetes, arthritis, or heart disease for example. All are diseases relatively new in human health.

“Right now, what we’re experiencing today in sedentary urban cities, that’s just a tiny blip on the scale of human evolution," Trumble said. “So, for 99 percent of the human experience we were living as hunter gatherers.”

When Trumble joined the study in the jungle he figured he’d find people were fit, but never imagined to this degree.

“On hunts with guys over the age of 80, they’d outrun me through the jungle and carry back giant boar," he said.

They rarely witnessed an overweight tribal member.

“They’re not eating processed food, they’re not drinking two or three sodas a day, they don't have any soda,” Gurven said. “Refined sugar consumption is very low, the meat is wild game, it's not factory farmed meat and they're eating lots of fish.”

(Photo courtesy of Ben Trumble and Michael Gurven)

Two men butchering a deer after hunting in the forest.

Both scientists caution, it’s not an endorsement to return to hunting and gathering food, especially if they consider the Tsimane’s risk for infectious diseases.

“More than two-thirds of Tsimane have parasites at any given time,” Trumble said. He attributes part of that to the Tsimane habit of running barefoot through the forests and eating wild game meat.

More than half of them are anemic.

“More than half in the study had high enough levels of inflammation that they would be in dangerous level in the U.S.," he said.

One half of the tribal members studied had hookworm, one-third giardia, and 20 percent had roundworm. Instead of fighting the parasites, the tribal members consider them "old friends," said Trumble.

“They're pathogens or parasites in particular that humans have co-evolved with for millennia,” Gurven said. “So, if you or I got giardia, we'd be in a lot of pain, the first thing we'd do is go to the doctor. Tsimane don’t have that luxury. It's not uncommon to watch a guy chopping trees for hours, just casually mentioning intestinal discomfort."

And, with each infection their immune system strengthens.

“So, you get less of an impact each time you get these infections and that's how vaccines work. Our body gets this immune response," he said.

Gurven warned, however, not to romanticize the Tsimane.

“Their life is hard and we can’t forget that we live longer lives than ever in the history of our species," Gurven said. "Things are pretty good."

Finding the balance between the two is what Trumble and his team hope to discover inside the frozen vials arriving at his ASU lab this summer.