Strange but True: Genes Responsible for Modern Maladies Evolved to Benefit Human Health
Suffering from health problems may be an uncomfortable experience but our ancestors appear to have also experienced some of these maladies.
Scientists have discovered that some modern health problems are very old, predating even the evolution of the Neanderthals, the Denisovans and contemporary humans.
Omer Gokcumen, a biologist from University at Buffalo's Department of Biological Sciences, said that his team's research, which was published in the journal Molecular Biology and Evolution on Jan. 2, showed that some genetic features that are linked with psoriasis, a chronic skin condition marked by rashes that burn and sting; the inflammatory bowel disease known as Crohn's disease and other aspects of human health are very old.
The researchers learned about this by comparing the genomes of modern humans to those of other closely related species that included chimpanzees and ancient human species that lived thousands of years earlier.
They were able to identify DNA chunks that exist in the chimpanzees but were erased in the evolutionary process. These so called deletions exist in the genomes of humans but are missing from others.
The unusually old deletions include those that are common in individuals who suffer from in Crohn's disease and psoriasis and those associated with a person's ability to respond to drugs.
"We found 17 exonic deletions that are shared with archaic hominin genomes, including those leading to three fusion transcripts," the researchers wrote. "The affected genes are involved in metabolism of external and internal compounds, growth and sperm formation, as well as susceptibility to psoriasis and Crohn's disease."
As to why certain health problems persisted for hundreds of thousands of years, it is because ancestors have evolved the genetic variations linked with certain health challenges to benefit human health.
Gokcumen cited sickle cell anemia as an example. He explained that the condition causes the red blood cells to take on a curved of crescent like shape that leads to deficiency of hemoglobin in the blood, but it also provides protection against the mosquito borne malaria by keeping the parasites out of the cells.
The new research likewise hints that very old deletions linked with Crohn's disease and psoriasis may have similar roles in terms of health.
"Crohn's disease and psoriasis are damaging, but our findings suggest that there may be something else - some unknown factor now or in the past - that counteracts the danger when you carry genetic features that may increase susceptibility for these conditions," Gokcumen said. "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."