Can Evolution Repeat Itself?
A press release from University of Chicago reported today that “115-million-year-old fossil of a tiny egg-laying mammal thought to be related to the platypus provides compelling evidence of multiple origins of acute hearing in humans and other mammals” (emphasis added in all quotes). The fossil apparently shows inner-ear bones in the monotreme lineage that supposedly diverged from the reptile-like ancestors of both marsupial and placental mammals.
Many paleontologists have doubted that such a seemingly complex adaptation could have originated more than once in mammals, but according to the authors of the paper, the evidence of T. trusleri [the reported shrew-size fossil] indicates that it did.
“Nothing like that has ever been found before,” said Tom Rich, PhD, lead author of the paper and curator of vertebrate paleontology at Museum Victoria in Melbourne, Australia.
They are claiming that the middle ear bones needed for acute hearing arose twice, independently, within mammals. “How can this supposedly rare and unexpected evolutionary change have occurred so commonly in early mammals?” the press release asks. James Hopson, one of the authors of the paper in Science,1 describes how this might have unfolded:
“Recent studies of jaw and ear function in primitive mammal-like reptiles indicate that the larger angular bone may have supported an eardrum while still part of the lower jaw,” Hopson said. But once the dentary bone made a new jaw hinge with the skull in the immediate predecessor of mammals, the accessory jawbones may have abandoned their job of supporting the jaw and evolved exclusively into the middle ear sound-transmitting function.
Hopson adds that “Only the evidence of fossils has been able to unravel this tangled history of a complex adaptation.” The only fossil evidence alluded to, however, is T. trusleri and extinct “mammal-like reptiles” without the adaptation, compared with living mammals and the platypus. The scientific paper itself is not sure the transition is clear: “because of the uncertain phylogenetic positions of these taxa with respect to true mammals (monotremes and theriiforms), none provides unequivocal support for the multiple origin of the definitive mammalian middle ear bones” – they only “suggest” the “possibility” of the idea. The paper also discusses uncertainty about the phylogeny of all these groups, and only provisionally builds its case based on one expert’s opinion, “because it is in accord with the polyphyletic origin of the definitive mammalian middle ear but requires the least amount of homoplasy in comparison with other proposed phylogenetic placements of monotremes.”
Martin and Luo in Science2 call this a “remarkable example of homoplastic evolution” (another term for convergent evolution, or the supposed independent evolution of similar structures). They call homoplasy a “major feature of evolutionary morphology.” This find, they say, answers a “fascinating but very difficult question facing evolutionary biologists” – that is, “whether a complex structure would be less likely than a simple structure to undergo independent homoplastic evolution.” From the tone of these articles, the only thing not in question by this find is evolution itself.
1Rich et al., “Independent Origins of Middle Ear Bones in Monotremes and Therians,” Science, Vol 307, Issue 5711, 910-914 , 11 February 2005, [DOI: 10.1126/science.1105717].
2Thomas Martin and Zhe-Xi Luo, “Homoplasy in the Mammalian Ear,” Science, Vol 307, Issue 5711, 861-862, 11 February 2005, [DOI: 10.1126/science.1107202].
As always, the independent variable in this equation is Darwinian evolution. Everything else must adjust to keep the story going. Improbabilities? No problem; just create new words like homoplasy that sound scientific, and toss a little pixie dust of natural selection to corral the lucky mutations for engineering complex systems as required.
This story looks uglier and uglier the more you peer below the surface to see the shenanigans the Darwin Party is pulling to make their pet theory look good in the face of monstrous problems. Take away the assumption of evolution and they have no leg to stand on. Time to blow the whistle on this scandal.