Genetic variants that damage the genome are associated with reduced reproductive success and an increased likelihood of not having children, suggests research.
According to researchers from the Wellcome Sanger Institute in the UK, one mechanism of natural selection that is removing damaging genetic variation from the population is increased childlessness.
It is likely linked to genetic influences on cognitive and behavioural traits, which may mean that men and women with these genetic variants are less likely to form reproductive partnerships.
However, the study, published in the journal Nature, also showed that this genetic link may play a very minor role in the overall likelihood of being childless. It accounts for less than one per cent when compared to more influential factors such as sociodemographic factors and choice.
In the study, the team included more than 340,000 participants, and investigated whether damaging genetic variants were associated with lower reproductive success by calculating for each person, how much damaging genetic variation they carry across their entire genome, known as their ‘genetic burden’.
They tested whether genetic burden was associated with the number of children that the participants had, and found it was associated with men with the highest genetic burden having an average 0.26 fewer children – but this was not seen in women.
The team also found that increasing genetic burden was associated with a higher chance of being childless in both men and women, but much more so in men.
“It’s important to emphasise that we have not found a ‘gene for childlessness’, as that implies a strong, causal effect of genetic variation on whether or not someone will have children. Instead we have shown that people with damaged genomes, particularly men, are slightly more likely to be childless,” said Eugene Gardner at the MRC Epidemiology Unit at the University of Cambridge.
“This is probably due to the effect of damaging genetic variants on cognitive and behavioural traits, which make these men less likely to find a partner to have children with,” said Gardner, who was at the Wellcome Sanger Institute while doing the research.
While the genetic burden is not associated with infertility, both men and women with a higher genetic burden were more likely to have mental health disorders.