Ghosts in our bones
Online Science Editor Vincent Plant discusses how Neanderthal DNA still impacts our lives
Neanderthals and humans have often interacted, mating with each other and exchanging genes. It is estimated that around two percent of our entire genome comes from Neanderthals rather than our Homo sapiens ancestors. Writing in Molecular Biology and Evolution, a team of scientists have shown that this had an impact on our fertility, specifically through the impact on one molecule- progesterone.
Progesterone is implicated in pregnancy and is encoded on chromosome 11 of the human genome. It works by binding to a receptor, which is itself encoded for by a gene known as the PGR gene. However, there are three different mutations to this gene both present in Neanderthal DNA and in modern humans, suggesting that we acquired them when humans and Neanderthals mated. These mutations are not necessarily inherited together and are present in one form or another in about 20% of non-Africans.
However, one of these mutations, known as V660L, has been shown to be fixed in the Neanderthal population, while the other two were not. Moreover, a study with almost half a million participants shows that one in three women has at least one copy of this mutated gene, inherited from long-dead Neanderthal ancestors. This result is about ten times higher than has been found for other Neanderthal genes. Clearly, one of the three has experienced a positive selective pressure. So why has this one difference been so successful?
one in three women has at least one copy of this mutated gene
Carriers of the V660L mutation have been shown to have more siblings, fewer miscarriages and reduced probability of bleeding in early pregnancy. The mutation has been shown to result in cells producing higher levels of progesterone receptor, indicating that it acts to boost overall fertility. This would explain why it is so prominent in populations today.
The mutation has been shown to result in cells producing more progesterone receptor
Neanderthals traditionally died out 30,000 years ago, around about the same time as humans migrated into Europe. However, their ghosts still survive in our DNA. In some ways, they are still very much alive.