- Men who have children later in life will find themselves with fewer grandchildren than younger dads, a new study who combed through centuries of census data. The results suggest that because children born to older fathers tend to have more potentially harmful genetic mutations than those with younger dads, they are less likely to pass on their genes. It seems natural selection works against older dads, weeding their descendants.
geneticists have shown that children born to older fathers tend to have new genetic mutations than those with younger dads. Most of these mutations are harmless but some may increase the risk of certain diseases.
For the daughter of a 17th century farmer, a mutation resulting in a weakened immune system or malfunctioning heart could have been an early death sentence or at least prevented him from having his own children. She was born in the 21st century, however, the chances of her living a long and productive life would be considerably higher, thanks to modern medicine. So are older fathers still the burden of changes they once were?
To find out, Ruben Arslan, a psychologist at the University of Göttingen in Germany, and colleagues analyzed data from the 17 census records and 18th century Germany, Canada, and Sweden, as well as a National population register of the 20th century in Sweden, looking over 1.3 million people in total. In both modern and pre-industrial populations, children born to older fathers have fewer children of their own who survived past age 5. For each decade an old father, his children had somewhere between 5% ( modern Sweden) and 13% (in the German population at the beginning) less children of their own, reports the team this month in a preprint available bioRxiv.org.
this seems a small price for any father, Arslan said, but when amplified by the hundreds of thousands of dads in a population, it has a real effect.
having fewer children of their own, the children of older fathers are less likely to transmit new mutations to future generations, eventually piling prevent these mutations in the population, said Martin Fieder, anthropologist at the University of Vienna who has not participated. "If children of older fathers do not reproduce, harmful mutations are removed from the gene pool."
This is not to say modern medicine is not having an impact. Over 99% Swedish babies now survive 1 year; it was 0 years ago, fewer than 0% have done This could help explain the slightly smaller effect of paternal age in modern Swedish population: babies born prematurely. or with birth defects are more likely to live.
So why the father's age still have an effect at all? At risk children could survive longer now, but that does not necessarily mean that they are able to reproduce when they reach adulthood, Arslan said they might struggle with infertility or have a condition like autism that makes it harder for them to find a partner. or, for some it might be deliberate: prospective parents who know their children are likely to inherit a certain mutation could decide to adopt instead
Arslan stressed that the results have a weight to the genetic makeup of the population as. together for many generations, but they should not deter a future father former self having children. "When we need at least 10,000 people in the samples to detect effects, you can imagine that this is fairly low risk."
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