New research shows that our ancestors have prodigiously mate with two other human-like groups that conferred on us some mixed genetic heritage.
The Neanderthals and the Davisonans were similar to early homo sapiens and new genetic evidence shows that all these groups have mated with each other. 4% of our genes come from the former and 4-6% from the latter group. Both groups had superior immunity to numerous pathogens and early homo sapiens absorbed these genes through natural selection.
“But the scientists think there was a downside. Inheriting Denisovan or Neanderthal immunity genes will have helped modern humans to fight the diseases of the day, but beyond the age of reproductive maturity they might have a more harmful effect, turning our immune systems on ourselves” – reports the Guardian.
So this added immunity benefit came at a hefty cost that many of us, including myself, bear today: beyond our early 20s homo sapiens has an increased tendency to develop autoimmune illnesses in which the body attacks its own tissues: thyroid tissues in the case of Hashimoto’s Thyroiditis, joint cartilage in the case of autoimmune arthritis, and insulin producing cells in Type 1 diabetes.
There is even a hypothesis according to which these genetic variants, alleles, in our genome, are actually somewhat foreign DNA that hadn’t evolved in our bodies and therefore could be considered slightly alien DNA that has a tendency to attack its host. A very kooky and amazing interpretation.
Just the idea that some of us struggle with debilitating autoimmune illnesses today because our ancestors have mated with other humanoid groups is enough to blow your mind.