Scientists believe they may have identified genetic variants associated with human fertility.
An international team of researchers, including scientists from the universities of Oxford and Cambridge, detected 43 regions of the genome – the complete set of DNA – containing variants associated with reproductive success.
The team found that variations in the gene ARHGAP27 were associated with having more children, but also with a shorter lifetime window of fertility.
The team also identified a region of the human genome that had been influenced by natural selection for thousands of years and continued to affect fertility.
Based on their findings, published in the journal Nature Human Behaviour, the experts said fertility was influenced by mechanisms that also affected both reproductive biology and human behaviour.
Professor Melinda Mills, director of Oxford’s Leverhulme Centre for Demographic Science, said: “This study is of interest to understanding changes in human reproduction over longer periods of time, reproductive biology and potential links to infertility.
“It also empirically tests one of the most gripping and fundamental questions asked by scientists across many disciplines and decades: Is there evidence of ongoing natural selection in humans and, if so, what is it and how does it operate?”
For the study, the researchers looked at data from nearly 800,000 individuals of European ancestry.
They also found the red hair colour gene – melanocortin 1 receptor (MC1R) – played a role in reproductive biology.
But the researchers clarified that the gene’s influence on the number of children a person may have was not related to the genetic mechanisms that affected pigmentation.
When comparing with ancient genome data, the researchers were able to identify a region of the genome – known as FADS1 and FADS2 – that had been undergoing natural selection for thousands of years.
According to the team, these genes are involved in producing specific fats that are key for human health and may have played a role in helping people in Europe to adapt to an agricultural diet.
The experts also believe that these genes still affect fertility today and that adaptation may be ongoing.
Dr Iain Mathieson, of the University of Pennsylvania’s Department of Genetics, in the US, said: “Independent evidence shows that the FADS region has been under selection in Europe for thousands of years.
“It represents the clearest example of a genetic variant with evidence of both historical and ongoing natural selection, though the reason for selection remains unclear.”
The researchers noted that their findings were limited to European ancestry and did not include other ethnicities.
Prof Mills said: “As with nearly 90% of contemporary genetic research, this study is limited by its use of data from only individuals of European ancestry.
“It is also related to our comparison with ancient DNA data as well in selecting the sample.”
She also added that not having data on other ethnicities was “problematic within the entire field” and the team had developed a Genome Wide Association Study Diversity Monitor to keep on top of diversity in genomics in real time.
