By Kudakwashe Phiri

The word Neanderthal conjures up imagery of simple, primitive, and prehistoric beings from a distant, almost unimaginable past. Contrary to popular belief, however, modern humans possess remnants of Neanderthal DNA within their genes. This is a result of Neanderthals and modern humans inter-breeding, meaning many non-African Europeans have Neanderthal gene variants within their DNA. We may not be able to physically see evidence of this tiny amount of Neanderthal DNA, but can it affect us in other ways, such as the ability to avoid miscarrying a pregnancy?

1 in 3 European women have neanderthal ancestry

A study that analysed data from the UK Biobank, which featured 244000 women, came to the conclusion that 1 in 3 European women have inherited the progesterone receptor gene from Neanderthals. Twenty-nine percent of modern women carried one gene receptor, whilst three percent carried two copies. “The proportion of women who inherited this gene is about ten times greater compared to other Neanderthal gene variants,” said Zeberg. The progesterone receptor leads to these women having an increased sensitivity to progesterone. This gene variant is important, as progesterone is known to affect the menstrual cycle and pregnancy. 

Progesterone is a vital steroid hormone produced by the ovaries. It is released during the menstrual cycle,  especially after ovulation, and prepares the body for pregnancy by thickening the uterine lining. If the egg is not fertilised then the menstrual cycle begins. However, if the egg is fertilised then the body creates more progesterone in order for the uterus to successfully implant an egg. During pregnancy, progesterone helps maintain the thickened uterine lining, nurturing the growing fetus by providing vital nutrients. The steroid hormone prevents muscle contractions in the uterus, which would otherwise lead to the body failing to accommodate the egg. Progesterone also reduces the chances of bleeding during the first trimester of pregnancy. Whilst light bleeding or spotting is not unusual during the implantation phase, bleeding during pregnancy could be a sign of complications. Therefore, the “pregnancy hormone” is very important for women trying to conceive, as too much or too little progesterone can lead to complications. 

The Neanderthal progesterone receptor is beneficial, as it is linked to increased fertility and more children. Other benefits of the Neanderthal receptor include fewer bleeds during the first trimester of pregnancy as well as fewer miscarriages. 

Unfortunately, unless a DNA test is conducted, many women will not know whether they possess this favourable Neanderthal gene variant. However, this discovery could explain why some women seem to be more fertile, or less likely to miscarry than others. 

Photo by Joshua Sortino on Unsplash