Humans nowadays survive much longer than our closest living relatives, chimpanzees, which rarely live past 50. Even hunter-gatherers—who often lack the advanced nutrition, modern medicine, and other benefits of industrialized living—have twice the life expectancy at birth as wild chimpanzees.

So what's changed in us since the days of our ape ancestors? Are we living so much longer mainly because of changes in our lifestyles or because of genetic mutations—in other words, evolution?

(Related: "Longevity Genes Found; Predict Chances of Reaching a Hundred.")

To find out how we got to this advanced state, the study team compared death rates in industrialized countries with those in modern-day hunter-gatherer groups, whose lifestyles more closely mirror those of early modern humans.

The researchers found that