Interbreeding With Neanderthals Gave Us A Stronger Immune System

A diagram of HLA inheritance. Interbreeding with Neanderthals
would have introduced a greater diversity of HLA gene

There has been a long standing theory which states that humans and Neanderthals interbred when they first met around 50,000 years ago. A recent study of our genome by a team led by Peter Parham from Stanford University School of medicine has shown that our strong immune system could have arisen from interbreeding with Neanderthals. The way our immune system works is coded in our DNA in what is known as the HLA group. These are components which dictate how our cells adapt to threats presented by bacteria and viruses.

By comparing the genomes of modern humans to those of the Neanderthals and Denisovans, the team now believes that only by interbreeding, could humans have achieved such a level of HLA diversity. The analysis shows that Neanderthal and Denisovan HLA genes make up more than half of the immune system related DNA in Europeans and Asians. The genes were introduced to Africa later, when agricultural migration from Europe into Africa occurred.

For example, the specific gene HLA-A appears in up to 95.3% of Papua New Guinea, 80.7% for Japan, 72.2% of China, 51.7 for Europe and 6.7 for Africa. The data could also shed light on how humans interbred and migrated. The research suggests two possible scenarios. The first is that interbreeding was widespread and frequent. The other, and the one supported by the research team, is that the genes were planted by maybe a few isolated cases which created seed groups. These would in turn pass on their modified genes to new populations.