Genetic decline is making people less fit over time: Should we worry?

It might seem counter-intuitive to anyone awed by the record-beating achievements of elite athletes like Usain Bolt, Femke Bol or Armand Duplantis, but genetic mutations are making humans less fit over the broad sweep of time.

Aiming to better understand the issue and to figure out how worried we should be, scientists in Germany and the UK have carried out what they said was "the first mutation accumulation experiment on a mammal."

Writing in the journal PLOS Biology, the researchers - from the University of Edinburgh and the Max Planck Institute - said that each generation sees spontaneous mutations which "introduce heritable changes that tend to reduce fitness in populations of highly adapted living organisms."

Ironically, 20th century progress in medicine, health care, science and sports training could be leaving humans even more vulnerable, as these advances offset the impact of natural selection, which has long been the countervailing force against ineluctable genetic entropy or decline.

The team said that while genetic mutations are typically "countered by natural selection," which ultimately removes most of them from the population, societal changes in recent decades, such as improvements in living conditions and health care, have "reduced the strength of natural selection."

Improvements to living standards have thereby increased the potential for "deleterious mutations" to accumulate, the researchers say.

According to estimates included in the PLOS Biology paper, humans could lose anything from 3% of fitness every 2 centuries to 5% per generation, depending on to what extent natural selection can function as a barrier and weed out the worst of the decline.

So should we be worried about an increasingly frail human species over time? Perhaps not, as the team said their experiments with mice mean that "even in the absence of natural selection, the rate of fitness loss should not be of concern." The researchers predict a 0.38% per-generation fitness decline among humans.

All the same, it is likely that more work needs to be done to better understand the issue, with the team explaining that their tests, which involved inbred mice, "did not assess the fitness effects of mutation accumulation in a natural environment."

Genetic mutations have been lined to the onset of diseases, with research published in recent weeks pointing to newly-discovered mutations in cancers and another mutation that appears related to Parkinson's.