Sex with Neanderthals weakened immune systems
EUROPE: Next time you get a cold, don’t feel sorry for yourself. Just consider it a penance - punishment for your ancestors’ overfondness for inter-species sex.
Scientists have found that the immune systems of people of African descent respond more strongly to infection than those of European descent, and the reason is - at least partly - because of Neanderthal genes.
It is generally accepted that people of different ancestry have differing levels of resistance to pathogens.
For two experiments, published in the journal Cell, researchers tried to identify why that would be - by isolating immune cells and exposing them to bacteria and viruses.
They found that in some cases those in people originating from Africa killed bacteria three times faster.
They also found that some of the genes involved in this response among Europeans came from Neanderthals.
When humans migrated from Africa into Europe, they found the continent was already occupied by Neanderthals. For thousands of years the two populations coexisted and, the genetic evidence shows, occasionally interbred, with the consequence being that modern Europeans all have a small proportion of Neanderthal DNA.
The research, by French, Canadian and US scientists, showed that part of that inheritance had given Europeans a lowered immune response.
However, they also said this was not necessarily a bad thing. The fact these genes were retained, and that others also seemed to have been under pressure to behave similarly, implied there may be a good reason for it.
‘‘The immune system of African Americans responds differently, but we cannot conclude that it is better, since a stronger immune response also has negative effects, including greater susceptibility to autoimmune inflammatory diseases such as Crohn’s disease,’’ Luis Barreiro, of the University of Montreal, said. Immune systems work partly by raising body heat to kill invaders.
‘‘Too much inflammation can damage organs and leave sequelae (complications). In short, a strong immune response can be beneficial in some areas but a disadvantage in others.’’ One explanation is that the pressure from pathogens is less in colder latitudes, meaning inhabitants’ bodies could afford to devote fewer resources to fighting bacteria and viruses. ‘‘I was expecting to see ancestry-associated differences in immune response but not such a clear trend towards an overall stronger response to infection among individuals of African descent,’’ said Professor Barreiro. The Times