Academic journal article The Science Teacher

Did Modern Maladies Help Our Ancestors Survive?

Academic journal article The Science Teacher

Did Modern Maladies Help Our Ancestors Survive?

Article excerpt

Psoriasis, a chronic skin condition, can cause rashes that itch and sting. So why would a genetic susceptibility to this and other ailments persist for hundreds of thousands of years, afflicting our ancient ancestors and us?

That's what scientists are asking after discovering that genetic variations associated with some modern maladies are extremely old, predating the evolution of Neanderthals, Denisovans (another ancient hominin) and contemporary humans.

"Our research shows that some genetic features associated with psoriasis, Crohn's disease, and other aspects of human health are ancient," says Omer Gokcumen, a University at Buffalo assistant professor of biological sciences.

Some of humanity's early ancestors had the telltale features, called deletions, while others did not, mirroring the variation in modern humans, the scientists found. This genetic diversity may have arisen as far back as a million or more years ago in a common ancestor of humans, Denisovans, and Neanderthals.

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The discovery highlights the importance of balancing selection, a poorly understood evolutionary dance in which dueling forces drive species to retain a diverse set of genetic features.

The research, published in Molecular Biology and Evolution, raises the possibility that the diseases in question--or at least a genetic susceptibility to them--"may have been with us for a long time," Gokcumen says.

One possible reason for this is that certain traits that made humans susceptible to Crohn's and psoriasis may also have afforded an evolutionary benefit to our ancient ancestors.

Though we often think of evolution as black and white--a trait is either good or bad--there are instances where the line is not so clear, Gokcumen says. …

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