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Modern humans enjoy a much longer life expectancy than their cousins the chimpanzees, mostly due to technology. Sanitary conditions, good nutrition and medicine have cut down our infant mortality rates.
However even our hunter-gatherer ancestors lived longer then other primates. This is likely to be a result of the difference in diet, says Professor Caleb Finch of the University of Southern California-Davis.
Early humans migrating into African savannas added more and more meat to their diet, first competing with scavengers and later as pack hunters. The energy-rich food allowed for the brain's development. But on the downside it opened way for a constant inflow of gut parasites.
"Over time, ingestion of red meat, particularly raw meat infected with parasites in the era before cooking, stimulates chronic inflammation that leads to some of the common diseases of aging," Finch explains.
Finch and his colleagues have pinpointed a unique human gene called apolipoprotein E (apoE3) responsible for transportation of cholesterol, which they call "meat-adaptive". It also regulates inflammation and a range of aging effects in the brain and arteries.
The researchers believe the gene has contributed to increasing human life spans.
At the same time another rare version of the same gene, the apoE4, is associated with aging diseases like cardiac diseases and Alzheimer's, increasing their risks several-fold.
"The puzzle is, if ApoE4 is so bad, why is it still present?" Finch asked. "It might have some protective effects in some other circumstances."
The biologists' study was published in the PNAS Early Edition magazine.
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