I recently picked up Galileo’s Finger: The Ten Great Ideas of Science by Oxford chemist Peter Atkins. It’s a 2003 book, and on the plus side, it offers enjoyable and concise explanations of many important scientific theories, including some lucid diagrams explaining Einstein’s ideas about relativity.
In his chapter on evolution, Atkins boldly states, “The effective prediction is that the details of molecular evolution must be consistent with those of macroscopic evolution.” (pg. 16) I’m willing to accept that “prediction.” However, Atkins unfortunately goes on to dramatically overstate the evidence for molecular evolution by asserting, “That is found to be the case: there is not a single instance of the molecular traces of change being inconsistent with our observations of whole organisms.” (pg. 16)
I’ve addressed this topic before, and, to put it nicely, Atkins’ comment is wrong. In fact, in 2000, Trisha Gura wrote an entire review article in Nature entitled “Bones, Molecules or Both?” (Vol. 406:230-233, July 20, 2000), devoted entirely to examining the difficulties encountered by evolutionary scientists when trying to reconcile molecule-based phylogenetic trees with phylogenetic trees based upon morphology. In Gura’s words, the commonality of these conflicts has led to great “evolution wars” among systematists over whether they should use “bones,” “molecules,” or “both” when constructing phylogenies. As Gura stated:
When biologists talk of the ‘evolution wars’, they usually mean the ongoing battle for supremacy in American schoolrooms between Darwinists and their creationist opponents. But the phrase could also be applied to a debate that is raging within systematics. On one side stand traditionalists who have built evolutionary trees from decades of work on species’ morphological characteristics. On the other lie molecular systematists, who are convinced that comparisons of DNA and other biological molecules are the best way to unravel the secrets of evolutionary history.
So can the disparities between molecular and morphological trees ever be resolved? Some proponents of the molecular approach claim there is no need. The solution, they say, is to throw out morphology, and accept their version of the truth. “Our method provides the final conclusion about phylogeny,” claims Okada. Shared ancestry means a genetic relationship, the molecular camp argues, so it must be better to analyse DNA and the proteins it encodes, rather than morphological characters that can end up looking similar as a result of convergent evolution in unrelated groups, rather than through common descent. But morphologists respond that convergence can also happen at the molecular level, and note there is a long history of systematists making large claims based on one new form of evidence, only to be proved wrong at a later date.
(Trisha Gura, “Bones, Molecules or Both” Nature, Vol. 406, pgs. 230-233 (July 20, 2000).)
There is a raging debate because these two types of data often conflict. Gura wouldn’t be discussing “evolution wars” if molecules and macromorphology were always in agreement regarding phylogenetic history. Consider these other striking comments from various scientists explaining the conflicts between molecule-based phylogenetic trees and morphology-based phylogenetic trees:
“As morphologists with high hopes of molecular systematics, we end this survey with our hopes dampened. Congruence between molecular phylogenies is as elusive as it is in morphology and as it is between molecules and morphology.” (Colin Patterson et al., “Congruence between Molecular and Morphological Phylogenies”, Annual Review of Ecology and Systematics, Vol 24, pg. 179 (1993).)
“That molecular evidence typically squares with morphological patterns is a view held by many biologists, but interestingly, by relatively few systematists. Most of the latter know that the two lines of evidence may often be incongruent.” (Masami Hasegawa, Jun Adachi, Michel C. Milinkovitch, “Novel Phylogeny of Whales Supported by Total Molecular Evidence,” Journal of Molecular Evolution, Vol. 44, pgs. S117-S120 (Supplement 1, 1997).)
“[T]he wealth of competing morphological, as well as molecular proposals [of] the prevailing phylogenies of the mammalian orders would reduce [the mammalian tree] to an unresolved bush, the only consistent clade probably being the grouping of elephants and sea cows.” (W. W. De Jong, “Molecules remodel the mammalian tree,” TREE, Vol 13(7), pgs. 270-274 (July 7, 1998).)
Atkins said there is “not a single instance” where molecule-based trees failed to confirm morphology-based trees. Yet a survey of the actual literature shows there is far more than “a single instance” of the molecular phylogenetic data conflicting with the phylogenetic data based upon whole organisms. As Trisha Gura put it, for some Darwinian scientists, the solution is simply “to throw out” the data that doesn’t fit the theory. Indeed, if we take Atkins’ “prediction” of Neo-Darwinism at face value, it seems that Darwinian evolution is faring poorly in this test.