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.

Vladimir Kremlev for RT (click to enlarge)

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.