Humans still elvolving - Study

Natural selection continues to weed out unfavourable traits in humans, which means humankind itself is continuing to evolve, but albeit a very slow rate showed a scale study.

These were the conclusions drawn from a large-scale study of genetic data sampled from 210,000 people from the US and UK.

Scientists from the University of Columbia and the University of Cambridge noted that genetic variants linked to Alzheimer’s disease and heavy smoking are rarer in longer-lived individuals.

Those whom longevity favoured also had fewer occurrences of heart disease, high cholesterol, obesity, and asthma.

The conclusions drawn were thus that these individuals’ genes had greater chances of being passed down and thus spread through the general population.

We find genetic evidence that natural selection is happening in modern human populations, said Dr. Joseph Pickrell, an evolutionary geneticist at Columbia and New York Genome Center who helmed the research effort.

New favourable traits evolve when genetic mutations arise that offer an advantage in survival. Members of each generation thereafter pass on those beneficial mutations, whereupon they and their adaptive traits become more common in the general population.

The scientists sampled the genomes of 60,000 individuals of European ancestry genotyped by Kaiser Permanente in California, and 150,000 people in Britain genotyped through the UK Biobank.

The researchers also determined that people genetically predisposed to delayed childbearing and puberty lived longer. A one-year puberty delay reduced the rate of death in both men and women by 3 to 4 percent. 

While the team believes these results are evidence that genetic variants that influence fertility are developing in certain American and British populations, they also caution that environment plays a role as well.

The environment is constantly changing, said lead author Hakhamenesh Mostafavi, a graduate student at Columbia.

A trait associated with a longer lifespan in one population today may no longer be helpful several generations from now, or even in other modern-day populations.

The study may the first to examine how the human genome is evolving in a period as short as one or two generations.

The study is published in PLOS Biology.