Phylogeny: Rewriting evolution : Nature News & Comment


Kevin Peterson grabs a pen and starts to scribble an evolutionary tree on the paper tablecloth of a bar in Hanover, New Hampshire. Drawing upside down to make it easier for me to see, he maps out the standard phylogenetic tale for placental mammals. First, Peterson scratches a line leading to elephants, which branched away from the rest of the placentals around 90 million years ago. Then came dogs, followed by primates (including humans) and finally rodents — all within a frenetic 20 million years. This family tree is backed up by reams of genomic and morphological data, and is well accepted by the palaeontological community. Yet, says Peterson, the tree is all wrong. 

A molecular palaeobiologist at nearby Dartmouth College, Peterson has been reshaping phylogenetic trees for the past few years, ever since he pioneered a technique that uses short molecules called microRNAs to work out evolutionary branchings. He has now sketched out a radically different diagram for mammals: one that aligns humans more closely with elephants than with rodents.

“I’ve looked at thousands of microRNA genes, and I can’t find a single example that would support the traditional tree,” he says. The technique “just changes everything about our understanding of mammal evolution”.

Peterson didn’t set out to rewrite textbooks. A mild-mannered but straight-talking Montanan, Peterson had made a quiet career studying how bilateral body plans originated more than 500 million years ago. He has a particular interest in marine invertebrates and had intended to stick with that relatively obscure branch of the animal tree. But a chance investigation of microRNAs in microscopic creatures called rotifers led him to examine these regulatory molecules in everything from insects to sea urchins. And as he continues to look, he keeps uncovering problems, from the base of the animal tree all the way up to its crown.

That has won him many critics, but also some strong supporters. “Peterson and his colleagues have demonstrated that microRNAs are a powerful tool in determining the relationships of major animal groups,” says Derek Briggs, director of the Yale Peabody Museum of Natural History in New Haven, Connecticut.

Now, together with his colleagues around the world, Peterson is putting it all on the line with mammals. “If we get this wrong, all faith that anyone has in microRNAs [for phylogenetics] will be lost,” says Philip Donoghue, a palaeobiologist at the University of Bristol, UK, who has teamed up with Peterson. And there is more at stake than just the technique. “It could well be the end of all our careers,” he says.

Written By: Elie Dolgin
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  1. This looks like science updating systems in the light of new evidence.  There were, and are, major revamps of some plant genera and species, as analysis of genotypes replaces phenotypic resemblance as a basis for classification.

  2. (P)eterson didn’t set out to rewrite textbooks.

    Silly journalist.  Of course he did.  If you’re not rewriting textbooks, you’re doing scientific research wrong.

  3. My major concern with using microRNA’s is that, while smaller, they tend to be vital in regulating gene expression at both local and global levels, so I would guess that their evolution is going to see larger spikes than a total genome one (in fact, a little closer to punnctuated evolution, lets hope Richard doesn’t read this comment :S), so I would give a little more credence to the traditional total genome.  Either way I’ll wait until the actual paper is published and the follow up research is done before forming any concrete opinions.

  4. “Tiny molecules called microRNAs are tearing apart traditional ideas about the animal family tree.”(Waits for someone to complain about “librul scientist” and their attacks on traditional family values).

  5. What is the deal with the comment about loosing a career
    if wrong??? If a scientist follows a field of research that is eventually shown
    to be wrong, then what is the harm? Even negative data is useful. The loss of a
    career from trying to learn and understand new data seems stupid to me. I
    hope science in general isn’t that foolish. It would be a tragic waste of some
    very bright minds.

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