Neanderthal gene increases fertility and reduces miscarriage

Women who carry a gene variant inherited from Neanderthal ancestors have fewer miscarriages, reduced bleeding events in pregnancy and increased fertility.

The research focused on a specific gene variant, namely PGR, that codes for progesterone receptors. Progesterone is a hormone that plays an important role in establishing and maintaining a pregnancy. Researchers found that the Neanderthal PGR gene variant is present in the genome of up to one-third of modern European women.

'The progesterone receptor is an example of how favourable genetic variants that were introduced into modern humans by mixing with Neanderthals can have effects in people living today' said lead author Dr Hugo Zeberg, of the Karolinska Institutet, Sweden and the Max Planck Institute, Germany.

In order to understand the influence this Neanderthal variant has on pregnancy, researchers analysed data from the UK Biobank. They discovered that women who possess the ancient variant were less likely to experience miscarriage or to bleed whilst pregnant. The study also found that such women had larger families, implying increased fertility.

The research team then further analysed the gene through data obtained from the Genotype Tissue Expression (GTEx) project, which revealed that carriers of the Neanderthal variant expressed a greater number of progesterone receptors on their cell surfaces. This, in turn, increases progesterone uptake, which may exert a protective effect on pregnancy.

While the identification of Neanderthal DNA in modern European and Asian genomes has been well documented, such genes tend to only exist in a small number of people. However, the team found that 29 percent of modern women inherit one copy of the PGR variant, whilst three percent acquire two copies.

The ancient PGR gene, which can be traced back as far as 40,000 years to an individual living in Tianyuan Cave, China, has likely resulted from human and Neanderthal interbreeding.

'The proportion of women who inherited this gene is about ten times greater than for most Neanderthal gene variants,' said Dr Zeberg. 'These findings suggest that the Neanderthal variant of the receptor has a favourable effect on fertility.’

This study was published in the journal Molecular Biology and Evolution.