Analysis finds strong match between molecular, fossil data in evolutionary studies

During a seminar at another institution several years ago, University of Chicago paleontologist David Jablonski fielded a hostile question: Why bother classifying organisms according to their physical appearance, let alone analyze their evolutionary dynamics, when molecular techniques had already invalidated that approach?

With more than a few heads in the audience nodding their agreement, Jablonski, the William Kenan Jr. Professor in Geophysical Sciences, saw more work to be done. The question launched him on a rigorous study that has culminated in a new approach to reconciling the conflict between fossil and molecular data in evolutionary studies.

For more than two decades, debate has waxed and waned between biologists and paleontologists about the reliability of their different methods. Until now, attention has focused on the dramatically different evolutionary history of certain lineages as determined by fossils or by genetics.

Scientists using molecular techniques assert that genetics more accurately determines evolutionary relationships than does a comparison of physical characteristics preserved in fossils. But how inaccurate, really, were the fossils? Jablonski and the University of Michigan's John A. Finarelli have published the first quantitative assessment of these assumed discrepancies in the Proceedings of the National Academy of Sciences.

They compared the molecular data to data based on the kinds of features used to distinguish fossil lineages for 228 mammal and 197 mollusk lineages at the genus level (both wolves and dogs belong to the genus Canis, for example).

No matter how they looked at it, the lineages defined by their fossil forms "showed an imperfect but very good fit to the molecular data," Jablonski said. The fits were generally far better than random. The few exceptions included freshwater clams, "a complete disaster," he said.

Jablonski and Finarelli (Ph.D.'07, University of Chicago), then decided to push their luck. They looked at the fits again, but this time focused on geographic range and body size. The result: a "spectacularly robust" match between the fossil and molecular data.

Jablonski interprets the results as good news for evolutionary studies. The work backs up a huge range of analyses among living and fossil animals, from trends in increasing body size in mammal lineages, to the dramatic ups and downs of diversity reported in the fossil record of evolutionary bursts and mass extinctions.

"Our study also points the way toward new partnerships with molecular biology, as we straighten out the mismatches that we did find," he said.

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	Gods Graves Glyphs	Thanks colorado tanker. University of Chicago paleontologist David Jablonski fielded a hostile question: Why bother classifying organisms according to their physical appearance, let alone analyze their evolutionary dynamics, when molecular techniques had already invalidated that approach? ...The question launched him on a rigorous study that has culminated in a new approach to reconciling the conflict between fossil and molecular data in evolutionary studies... Until now, attention has focused on the dramatically different evolutionary history of certain lineages as determined by fossils or by genetics... No matter how they looked at it, the lineages defined by their fossil forms "showed an imperfect but very good fit to the molecular data," Jablonski said. The fits were generally far better than random. The few exceptions included freshwater clams, "a complete disaster," he said... They looked at the fits again, but this time focused on geographic range and body size. The result: a "spectacularly robust" match between the fossil and molecular data... The work backs up a huge range of analyses among living and fossil animals, from trends in increasing body size in mammal lineages, to the dramatic ups and downs of diversity reported in the fossil record of evolutionary bursts and mass extinctions. The main problems with the genetic approach are psychological -- overreliance on modeling and computer simulations, overgeneralization (mutation rates, stabilities), and inability to see the limits of using surviving DNA to tell anything about either its geographic origin or its antiquity. Obviously, areas with high infant mortality and fairly low birth rates (such as much of Africa) and/or tribal affiliation will show a skew toward supposed antiquity, simply because areas with agricultural surpluses of great antiquity (typically the riverine societies) will greatly expand the number of descendants of any one mating pair. The Neandertal Enigma by James Shreeve "Allan Wilson had always been described to me in superlatives, such as 'one of the real geniuses in science,' or 'the most arrogant guy I know...' [H]e apologized for putting me off so long and bluntly explained that the reason he had done so was that he did not trust me... 'The anthropological perspective on evolution is no longer valid; it has been overthrown. And yet the science writers who insist on talking to me come drenched in an anthropological perspective, and there is really no point in talking to them... It is paralytic. It prevents you from asking certain questions, and it forces you to ask others. The whole discipline invites you not to investigate.' ...A few months before my visit, Wilson had announced at the annual meeting of the American Association for the Advancement of Science... that the Neandertals were replaced because they could not speak... suggesting that a particular gene for language might have been carried in the mitochondria themselves. Since invading males would have been more likely to mate with resident females than the other way around, the offspring of sexual contact between the two groups would be 'linguistically deaf-mute,' like their Neandertal mothers. Thus disadvantaged, these 'village idiots' would face the same fate as the mothers: extinction. Only the language-endowed African lineage would continue. The language gene idea, and especially the unfortunate term 'village idiots,' elicited hoots of derision from the anti-Eve camp, and gave no joy to Wilson's colleagues." [pp 119-121] To all -- please ping me to other topics which are appropriate for the GGG list. GGG managers are SunkenCiv, StayAt HomeMother, and Ernest_at_the_Beach
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If I understand this correctly, they should not get so excited so quickly. Improved fit between molecular and phenotypic data will another beast liberals are afraid to name: Racism.

You see, the whole race-and-genetics argument fell apart the finer the structure you looked at. Well meaning bio-anthropologists started with attempting refined systems of racial classification. As the number of measures and categories grew, the ability to maintain cleanly separated racial categories became harder and harder to maintain. This contributed to debunking notions of IQ and race.

The take home message was that racial categories were superficial, and told you nothing biologically - other than some basic examples of environmental adaptation.

Now, by being able to establish a smooth continuum of significance from the molecular to the phenotypic, there will be a return to “racial analysis.” Let the fireworks begin.

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