But it nagged at him that the classic thrifty-gene theory, which he now calls "a relic," applied to former hunters when the Pima had been successful farmers of beans, squash and cotton. Only after ranchers diverted the river that watered their crops, followed by a drought and the start of their sedentary life on a reservation, did famine persist.
By the early 1900s, Prof. Benyshek says, they were dying of scurvy and starvation. So, when he first read about the origins theory in the early 1990s, he suddenly saw the Pima story "as the perfect storm." Babies born to the malnourished Pima women of the 1920s and 1930s were already on the road to developing diabetes, he believes, and passing on that higher risk to the next generations.
"We're arguing now that diabetes is a political, economic disease," he says, "due directly to the deprivation they suffered."
Dogrib dodge the bullet
If the origins theory reveals why the Pima have so much diabetes, Emöke Szathmáry, former president of the University of Manitoba and a biological anthropologist, suspects that it also helps to explain why the Dogrib people of the Northwest Territories have so little.
The Dogrib were once nomadic hunters who lived off caribou and fish, but fur trapping for Europeans allowed them to add flour, baking powder, sugar and tea to their diet as early as the 19th century. Yet even in 1979, Dr. Szathmáry found no cases of diabetes among them, and the prevalence of the disease, according to one recent study, remains low even today.
She suspects that they are in part protected by history: Gold mining and the war delayed their settlement into permanent communities until after the 1950s.
"About 75 per cent of my sample had spent their childhoods on the land, in the sub-Arctic," she says. "They were physically active" - and born to women who lived the same way.
"The trajectory was laid down in utero."
Carolyn Abraham is The Globe and Mail's medical reporter.