Some modern illnesses and disorders including diarrhea and itchy skin could have provided health benefits to our ancient ancestors, new research has found.

Sickle cell anemia is a condition marked by the formation of blood cells shaped like crescents, instead of a disk, which is normal. This unusual form of the cell can stick to blood vessels, blocking oxygen flow to organs, which can lead to disastrous consequences. However, this disorder provides an unexpected benefit to afflicted people, protecting them against malaria. The condition supplies this protection by preventing parasites from attacking the cells.

Crohn's disease, an often painful disease marked by inflamed bowels, and psoriasis, a common skin rash, both afflicted our human ancestors, the study found.

The genetic code of chimpanzees was examined, and compared to both ancient and modern humans. Researchers were especially interested in deletions -- bits of code that are present in all chimpanzees, but are not seen in most early or modern humans. Some of these deletions are responsible for psoriasis and sickle cell anemia.

"Both diseases are autoimmune disorders, and one can imagine that in a pathogen-rich environment, a highly active immune system may actually be a good thing even if it increases the chances of an auto-immune response," Omer Gokcumen of the University at Buffalo said.

Psoriasis can be found in various forms today, but the most common variety is known as plaque psoriasis. The disease is characterized by the development of red, itchy, skin rashes which typically form on elbows, knees, scalp, palms, and soles of the feet. The disease is not contagious, and occurs in equal numbers of men and women.

Crohn's disease is one of the two most common forms of inflammatory bowel disease (IBD). The disorder can affect both the large and small intestines of people suffering from the condition. In patients with IBD, their immune system mistakes food for a foreign body, and attacks.

A balance may have evolved in the human body between protecting bodies and discomfort or other significant health risks. This means the same conditions many people are treated for today once protected our ancestors.

"We're thinking forces that maintain variation might be more relevant to human health and biology than previously believed," Yen-Lung Lin, a doctoral candidate at the University of Buffalo, said.

This study highlights the idea that evolutionary adaptations are rarely purely advantageous or detrimental.

Study of how modern maladies may have evolved as means of protecting health in our ancient ancestors was profiled in the journal Molecular Biology and Evolution.

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