Thursday, December 17, 2009

Meat May Be The Reason Humans Outlive Apes

meatGenetic changes that apparently allow humans to live longer than any other primate may be rooted in a more carnivorous diet.

These changes may also promote brain development and make us less vulnerable to diseases of aging, such as cancer, heart disease and dementia.

Chimpanzees and great apes are genetically similar to humans, yet they rarely live for more than 50 years. Although the average human lifespan has doubled in the last 200 years — due largely to decreased infant mortality related to advances in diet, environment and medicine — even without these improvements, people living in high mortality hunter-forager lifestyles still have twice the life expectancy at birth as wild chimpanzees do.

These key differences in lifespan may be due to genes that humans evolved to adjust better to meat-rich diets, biologist Caleb Finch at the University of Southern California in Los Angeles suggested.

The oldest known stone tools manufactured by the ancestors of modern humans, which date back some 2.6 million years, apparently helped butcher animal bones. As our forerunners evolved, they became better at capturing and digesting meat, a valuable, high-energy food, by increasing brain and body size and reducing gut size.

Over time, eating red meat, particularly raw flesh infected with parasites in the era before cooking, stimulates chronic inflammation, Finch explained. In response, humans apparently evolved unique variants in a cholesterol-transporting gene, apolipoprotein E, which regulates chronic inflammation as well as many aspects of aging in the brain and arteries.

One variant found in all modern human populations, known as ApoE3, emerged roughly 250,000 years ago, "just before the final stage of evolution of Homo sapiens in Africa," Finch explained.


Full story here.
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