Humans are evolving more rapidly than previously thought, according to the largest ever genetics study of a single population.
Scientists reached the conclusion after showing that almost every man alive can trace his origins to one common male ancestor who lived about 250,000 years ago. The discovery that so-called “genetic Adam”, lived about 100,000 years more recently than previously understood suggests that humans must have been genetically diverging at a more rapid rate than thought.
Kári Stefánsson, of the company deCODE Genetics and senior author of the study, said: “It means we have evolved faster than we thought.”
The study also shows that the most recent common male ancestor was alive at around the same time as “mitochondrial Eve” – the last woman to whom all females alive today can trace their mitochondrial DNA.
Unlike their biblical counterparts, genetic Adam and Eve were by no means the only humans alive, and although they almost certainly never met, the latest estimate which gives a closer match between their dates makes more sense, according to the researchers.
When the overall population size is stable – as it has been for long periods in the past – men have, on average, just one son, and women, just one daughter. This means that for any given man, there is a high chance that his paternal line will eventually come to an end. This means any male descendants, for instance his daughter’s son, would have Y-chromosomes inherited from other men. If you travelled back far enough in time, the theory goes, there would be only one man whose paternal line extends unbroken to the present day: this man is Y-chromosome Adam.