Human longevity largely a modern phenomenon

By Rachel Ehrenberg

Web edition: October 15, 2012
Print edition: November 17, 2012; Vol.182 #10 (p. 10)

Despite what the fashion magazines tell you, 40 isn’t the new 30. Seventy is.

A new study finds that humans are living so much longer today compared with the rest of human history that the probability of dying at 72 is similar to the death odds our ancestors likely faced at 30.

This uptick in longevity is quite recent — occurring in the last century and a half — which suggests it has little to do with genes, starvation diets or anti-aging miracle drugs. Rather, it is likely due to eliminating environmental dangers faced by Homo sapiens of old, an evolutionary anthropologist and his colleagues argue online October 15 in the Proceedings of the National Academy of Sciences. Sanitation measures that clean up drinking water, regular access to food, plus antibiotics and vaccines seem to go a long way toward fighting off death.

“It’s striking,” says Ronald Lee, an economist at the University of California, Berkeley who specializes in demographics and aging. “We already think of humans as a really long-lived species,” says Lee, who wasn’t involved in the study. “It raises the question of how far we can go.”

Evolutionary anthropologist Oskar Burger and his team wanted to study human longevity in an evolutionary context. So they turned to previously gathered data on chimpanzees, hunter-gatherer societies in parts of Africa and South America and numbers from the Human Mortality Database for Japan, Sweden and France.

The data reveal a steady, gradual drop in the probability of dying relatively young that begins just before 1900 for the French and Swedes. But the mortality numbers for hunter-gatherers remain closer to wild chimpanzees than to these westernized societies. However, when the researchers looked at hunter-gatherer groups who received some western medicine and occasional help with food, the mortality in those groups dropped, widening the gap between them and chimps and bumping them up to numbers comparable with pre-1900 Sweden and France.

“It’s amazing what clean water and a bit of extra food gets you,” says Burger, of the Max Planck Institute for Demographic Research in Rostock, Germany.

A 30-year-old hunter-gatherer has the same probability of death as a Japanese person today who is 72 years old, the study found. At 15, a hunter-gatherer has a 1.3 percent chance of dying in the next year; Swedes hit those odds at age 69.

Surprisingly, the research also suggests that there’s room for improvement, and that the upper limit on healthy human living has yet to be reached. Aging theory suggests that the biological machinery should increasingly break down once a person passes the age of reproducing and caring for young (SN: 10/20/12, p. 16). But for some reason, humans seem to have become exceptionally good at dodging that bullet.

And researchers may even be able to extend human lifespans even longer with insights from ongoing research into the cellular switches and genes that extend the lives of roundworms and rodents in the lab.

“It may not be that difficult to continue to slow the rate of mortality,” says molecular biologist Brian Kennedy of the Buck Institute for Research on Aging in Novato, Calif. “I still believe very strongly that it’s going to be possible to manipulate healthy lifespan.”