4Comments
A study earlier this week controversially claimed that all humans were descended from a single couple, but that claim has now been contested.
The study on which this claim was made was actually first published in the journal Human Evolution back in May this year. In it, scientists from The Rockefeller University in New York looked back to between 100,000 and 200,000 years ago, when they said an unknown extinction event might have taken place, reducing the population of many species including humans dramatically
“The 0.1 percent average genetic diversity within humanity today corresponds to the divergence of modern humans as a distinct species about 100,000 to 200,000 years ago,” they said, “not very long in evolutionary terms. The same is likely true of over 90 percent of species on Earth today.”
The findings were based on a technique called DNA barcoding, which can identify a species from a short DNA sequence, preferably in mitochondria. In the study, they looked at more than 5 million mitochondrial barcodes from more than 100,000 animal species.
For some reason that is not entirely clear, though, some outlets appear to have misconstrued the results into thinking all of humanity came from a single pair of adults, obviously drawing comparisons to Adam and Eve.
But as Michael Marshall points out at Forbes, this is not true at all. “[T]he study they rest on does not demonstrate anything of the kind, and other lines of evidence strongly suggest that past human populations were always much larger than two,” he said.
He pointed to some reasons why this was not the case. First, it is difficult to draw big conclusions from mitochondrial DNA. Second, there is no evidence for a large extinction-level event 200,000 years ago. And the claim of the study that an event occurred between 100,000 to 200,000 years ago “is so vague as to be meaningless”.
Plus, it’s noted the researchers only ever said their findings were “consistent” with there being a founding pair of humans, not that they’d actually found a pair. Coupled with evidence that humans are as old as 500,000 years, the findings of this study seem shaky at best.
As with anything in science, always remember that – as the late Carl Sagan said – extraordinary claims require extraordinary evidence. There are a lot of interesting and legitimate stories out there, but always keep that skeptical hat at the ready, just in case.
