Ancient Human-Chimp Link Pushed Back Millions of Years

Jun 16, 2014

By Dan Vergano

 

Humanity’s genetic split from an ape-like ancestor came about 13 million years ago, far earlier than the long-supposed era of a common ancestor of early humans and apes, suggests a first study of chimp gene mutations.

Along with shining a new genetic light on human origins, the findings published on Thursday in the journal Science point to the role that evolution plays in fostering mutations, some linked to inherited diseases, in our genes.

On the surface, this and other recent studies contradict the general consensus suggested by the fossil record: that the last common ancestor of the two species, a flat-footed ape, lived some seven million years ago.

But both observations could still be true, said paleoanthropologist John Hawks of the University of Wisconsin, Madison, who was not involved in the new study. The ape-like common ancestor species might have endured until 7 to 10 million years ago, long after the genetic split between chimps and humans, he said.

That would largely explain the difference seen between gene-based and fossil-based estimates of the date the species diverged.

“We also don’t know if mutation rates varied widely in the ancient past; maybe they were different than now,” says study senior author Gil McVean of the United Kingdom’s Wellcome Trust Centre for Human Genetics in Oxford.

That could also change estimates of the age of an ancestral genetic split between men and chimps. “That’s something only looking at more primates might help tell us,” McVean says. (See video: “Curious Chimp.“)

Chimp Mutation Rates

According to the analysis released Thursday, the promiscuity of chimps seems to drive a higher genetic mutation rate in chimp males. Gene mutations in chimp offspring also greatly increases with the age of the ape father. (See video: “Baby Chimp.”)

“You really don’t want an older chimp as a father,” says McVean. “The vast majority of mutations are, at best, neutral,” he says, though some can be “very harmful.”

Chimps and people share about 99 percent of their DNA, making them our closest living genetic relatives. The rate at which human genes are altered, or mutate, has come under wide study in the past five years. Some studies have raised concerns about older fathers passing disease risks on to their children. But in chimps, the generational mutation rate was uncertain, until now.

5 comments on “Ancient Human-Chimp Link Pushed Back Millions of Years

  • According to the analysis released Thursday…

    Oh for God’s sake, this one bit of research is barely a week old, and already it’s being treated as established. Goldacre, why do you continue to be relevant?

    And last, in our brief taxonomy, is the media obsession with “new breakthroughs”: a more subtly destructive category of science story. It’s quite understandable that newspapers should feel it’s their job to write about new stuff. But in the aggregate, these stories sell the idea that science, and indeed the whole empirical world view, is only about tenuous, new, hotly-contested data. Articles about robustly-supported emerging themes and ideas would be more stimulating, of course, than most single experimental results, and these themes are, most people would agree, the real developments in science. But they emerge over months and several bits of evidence, not single rejiggable press releases. Often, a front page science story will emerge from a press release alone, and the formal academic paper may never appear, or appear much later, and then not even show what the press reports claimed it would (www.badscience.net/?p=159).

    Gene studies regularly throw up the odd gene locus comparison that doesn’t map perfectly with the two species’ time of divergence (technically three species, since an outgroup species is also used for comparison), but genetics proceeds by comparing multiple locii and finding which tree is most parsimonious. You don’t just take one of these studies and go “OMG new breakthrough science changing its mind whodathunkit”.

    Until this goes further than a few days of publicity without being shot down or dismissed as business as usual in the lab, I’ll stick to the consensus that the split occurred around 6 or 7 million years ago, since that’s what prior genetic and palaeontological studies collectively suggest.



    Report abuse

  • So the most recent common ancestor of humans and chimps was a species that lived from X to Y million years ago with X < Y, we already knew X, we’ve found out Y and the fact that Y is bigger than X is treated in the headline as “we got X wrong”, only for the article to admit the truth. This is why I hate journalists. They’re the only group who think saying a lie, than admitting it’s a lie a few sentences or few dozen sentences later, is all right.



    Report abuse

  • Totally agree with the previous comments on the general poor state of science journalism. I guess this reflects general public perception as a whole – ‘new study x refutes old idea y’ will attract more interest than ‘new study x extends the possible range of previous idea y’.

    In any case wasn’t the speciation of human ancestors and chimp ancestors likely to be a ‘messy affair’, drawn out over a significant time-period rather than a single well-defined event? It would be interesting to hear a specialists viewpoint on that with regard to what level of accuracy/precision can realistically be attained when it comes to pinning down a timeframe for the human/chimp last common ancestor.

    Also – given the mention of this in the original piece: “We also don’t know if mutation rates varied widely in the ancient past; maybe they were different than now” – I wonder what the error ranges are on the ’13 million years’ speciation estimate in this particular study, irrespective of the messy nature of the event(s)?

    It would help a lot if these things were discussed more in the media as a whole so that the general public can become accustomed to how scientific data should actually be presented. As mentioned by Zeuglodon, at least Ben Goldacre is trying his best at getting these things out there, but its a shame that science journalists seem to have largely immunised themselves from his criticisms/advice.



    Report abuse

Leave a Reply

View our comment policy.