This article was updated at 7:19 p.m. ET.

Humans are living longer than ever, a life-span extension that occurred more rapidly than expected and almost solely from environmental improvements as opposed to genetics, researchers said today (Oct. 15).

Four generations ago, the average Swede had the same probability of dying as a hunter-gatherer, but improvements in our living conditions through medicine, better sanitation and clean drinking water (considered "environmental" changes) decreased mortality rates to modern levels in just 100 years, researchers found.

In Japan, 72 has become the new 30, as the likelihood of a 72-year-old modern-day person dying is the same as a 30-year-old hunter-gatherer ancestor who lived 1.3 million years ago. Though the researchers didn't specifically look at the United States, they say the trends are not country-specific and not based in genetics.

Quick jump in life span

The same progress of decreasing average probability of dying at a certain age in hunters-gatherers that took 1.3 million years to achieve was made in 30 years during the 21st century.

"I pictured a more gradual transition from a hunter-gatherer mortality profile to something like we have today, rather than this big jump, most of which occurred in the last four generations, to me that was surprise," lead author Oskar Burger, postdoctoral fellow at the Max Planck Institute for Demographic Research in Germany, told LiveScience.

Biologists have lengthened life spans of worms, fruit flies and mice in labs by selectively breeding for old-age survivorship or tweaking their endocrine system, a network of glands that affects every cell in the body. However, the longevity gained in humans over the past four generations is even greater than can be created in labs, researchers concluded. [Extending Life: 7 Ways to Live Past 100]

Genetics vs. environment

In the new work, Burger and colleagues analyzed previously published mortality data from Sweden, France and Japan, from present-day hunter-gatherers and from wild chimpanzees, the closet living relative to humans.

Excerpt from:

Human Life Span Took Huge Jump in Past Century