How to maintain a healthy heart is a surprisingly contentious question. Diet and exercise are crucial, everyone agrees — but the ideal specifics and the relationships among them remain mysterious. Some experts recommend avoiding dietary fats; others endorse fat and low carbohydrates. The impact of high levels of inflammation on heart disease is disputed. And almost no one can agree about how much (or what type of) exercise is optimal.

But a study published last month in The Lancet points the way to resolving some of these issues by focusing on the Tsimane, a group of subsistence farmers and hunters living in Bolivia along a tributary of the Amazon River.

Anthropologists have learned a lot about the lives of the Tsimane since they began studying them 15 years ago. The men typically spend seven hours or so of every day hunting, fishing or poling their canoes to towns to sell and procure food. The women devote almost as much time to gathering nuts and farming rice, corn and plantains. Men and women each cover roughly eight miles, or 17,000 steps, each day.

Their diet is heavy on carbs: 72 percent of their daily calories derive from unprocessed starches, 14 percent from saturated and unsaturated fats and 14 percent from protein. Many Tsimane experience frequent infections and show chronically elevated levels of inflammation.