Another Look at the Latest Blow to the Darwinian Tree of Life, and the Man Who Dealt It - Evolution News & Views

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Another Look at the Latest Blow to the Darwinian Tree of Life, and the Man Who Dealt It

Kevin Peterson.jpg

How many times can evolutionists say everything they know is wrong before people start to really believe it?

As Casey Luskin noted here earlier, a news article in Nature tells the tree-shaking story of Kevin Peterson. This whole subject is so delightful it deserves another look.

A molecular paleobiologist at Dartmouth, Peterson never set out to disturb fellow believers in Darwinian theory. He just thought he would try a new method for constructing phylogenetic trees: tracking relationships via micro-RNAs. Peterson thought micro-RNAs would be a good marker of evolutionary relationships:

MicroRNAs, Peterson and [colleague Lorenzo] Sempere discovered, are unlike any of the other molecular metrics that biologists typically use to tease apart evolutionary relationships. DNA binding sites, for example, continuously mutate; microRNAs, by contrast, are either there or they aren't, so their interpretation doesn't require such complex sequence and alignment analyses. And once gained, microRNAs usually remain functional, which means that their signal stays intact for hundreds of millions of years.
But when Peterson tested the conventional Darwinian tree of life for rotifers, his tree didn't match the conventional one. That was only the beginning. He found tree rot all over:
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.
Peterson's observations, first published in a minor journal but now getting notice in Nature and Science, are winning him some vocal critics, but mostly reluctant supporters. His work on the family tree of placental mammals will be his latest unsettling contribution. Peterson had decided to lay it all on the line by testing the family tree of mammals. "We're mammals, so this matters," he said. Sure enough, problems are surfacing there, too.

The data's refusal to cooperate with other Darwinian phylogenies has left Peterson "up a tree," as Nature writer Elie Dolgin quips: "At first, Peterson was shocked by his results, which still haven't been published. But he has spent the past year validating his tree with gene-expression libraries and genomic sequences, all of which he says support his findings." He's being extra careful, because "If we get this wrong, all faith that anyone has in microRNAs [for phylogenetics] will be lost," his colleague Philip Donoghue, a palaeobiologist at the University of Bristol, said. "It could well be the end of all our careers."

The reactions of other scientists have been entertaining:

  • "One of the reviewers said it was impossible, what we were describing," Peterson said.
  • "He's talking about the entire genome that has to be wrong."
  • "I don't give it any serious consideration. There have to be other explanations."
  • "What we know at this stage is that we do have a very serious incongruence. It looks like either the mammal microRNAs evolved in a totally different way or the traditional topology is wrong. We don't know yet."
Stirring controversy was not Peterson's intention. Dolgin describes him as a "mild-mannered but straight-talking Montanan" who "didn't set out to rewrite textbooks."
For now, he's trying to amass the best evidence he can before publishing the mammal study. Then he wants to return to the quiet life of an ancient-invertebrate biologist. But if Peterson's voyage upends the mammalian phylogeny, he'll have left a furry mess in his wake.
Why is this so surprising to anyone? In fact, it's old news. Since the first molecular studies with proteins like cytochrome C and other molecules, neo-Darwinists have repeatedly generated trees that conflict with each other depending on the marker used. Over and over, they have had to explain away these observations. There is so much wiggle room in the methods that some have invoked epicycle-style fudge factors like "rate heterogeneity" (molecular clocks ticking at different rates) to keep the data in sync with the theory.

This is a classic example of theory directing data, instead of the other way around -- a form of the plaustrum ante equum (cart before the horse) fallacy. The fallacy becomes evident when different practitioners with the same theory generate contradictory data sets and have to invoke fudge factors to avoid changing their assumptions. You notice that Nature titled its article "Phylogeny: Rewriting evolution," not "Phylogeny: Falsifying evolution."

Trying to play the unbiased scientist, Peterson said, "Ultimately, I don't really care how mammals are related to one another -- it doesn't matter to me. But what does matter is the validity of the data set." That's a commendable attitude, but would he be equally comfortable questioning neo-Darwinian theory itself?

Intelligent-design advocates are unsurprised by any of this, because their focus is on the origins of functional information, not unobservable prehistories imagined by assuming that a universal common ancestor gave birth to a family tree via random mutation and natural selection. Design theorists also believe in following the evidence where it leads.

Image credit: Dartmouth College.