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23rd February, 2009

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Big birds rat on evolution theory

I admit creationists can talk through their hats at times, particularly those who assert that everything, including dinosaurs and trilobites, were made only six to ten thousand years ago. But I cannot help but be swept off my feet sometimes by the boundless - and unwarranted - confidence of diehard evolutionists. This year they are serving up their vinegary champagne in double-sized flutes.

Case in point. In its paean to Darwin, The February edition of "Smithsonian" talks about Darwin's disquiet over "the existence of oddly similar terrestrial species on separate continents". How could, say, the flightless, long-necked emus and cassowaries of Australia, ostriches of Africa, kiwis of New Zealand, and rheas of South America - birds so similar in body plan that they must surely be derived from a common ancestor — end up on separate continents separated by huge swathes of ocean? The Smithsonian provides its glib answer to this worrisome puzzle: "Continental drift, proposed in 1912 and confirmed in the 1960s, shows how descendants of a common ancestor were separated when landmasses moved". Way back when those continents were all joined together in the great southern landmass of Gondwana the alleged common ancestor of all these birds (never mind the complete lack of fossil evidence for the existence of such a Big Beak) strutted boldly across the supercontinent. As Gondwana began to gradually break up, populations of the supposed ancestor became isolated from one another providing them the geographic isolation needed to evolve into the unique forms found on today's continents. Contra Smithsonian's upbeat assertions, this old theory has been unraveling for some years. As Olson said back in 1985, "The origin and relationships of the paleognathus [referring to their unique palate] ratites and tinamous is the most contentious issue in avian systematics" (p. 96).1 Probably still is.

Smithsonian's confidence belies the serious problems posed to evolution theory by these birds, known as ratites, which are characterized by the unique structure of their palate (an attribute shared with tinamous) and the lack of the large keel which provides the anchor for the wing muscles found on the sternum of all other birds. Truth is, all is definitely not well in ratite-evolution land.

First, consensus hasn't been reached as to whether all ratites have one common ancestor (monophyly) or whether they each descended from a different ancestor (polyphyly). In 1996 Alistair Dawson said that, "Contrary to earlier beliefs. DNA-DNA hybridization studies suggest that the ratites comprise a monophyletic taxon".2 Most would agree. Some facts seem to provide indisputable evidence of a single origin. Ratite sex chromosomes are quite different from those found in all other birds, a fact that is difficult to reconcile with any theory of multiple origins.3 However, a very recent report argues otherwise:

The prevailing view is that ratites are monophyletic with the flighted tinamous as their sister group, suggesting a single loss of flight in the common ancestry of ratites. However, phylogenetic analyses of 20 unlinked

nuclear genes reveal a genome-wide signal that unequivocally places tinamous within ratites, making ratites polyphyletic and suggesting multiple losses of flight.4

So this up-to-date report argues for multiple origins of ratites, and multiple cases of reverse evolution (the loss of flight). If this received widespread acceptance among evolutionists it would provide a completely different answer to Darwin's puzzle than the one presented in Smithsonian. What you have, instead, is convergent evolution - completely different lineages of creatures evolving similar structures by pure coincidence.

Practically any idea that can be offered for the origin/s of ratites has been. Olson lists five theories, then adds, "At this point there is no real proof for any of the various origins proposed above" (p. 103). One breathtaking proposal for the origin of the ratite palate and lack of a keel suggests that these structures did not evolve from the "normal" condition through a process of loss; rather, what really evolved was a condition of permanent juvenility. All birds develop a ratite-like palate of sorts and a keel-less sternum during embryonic development. Dawson suggests that, "In short, adult ostriches. are simply overgrown chicks. they are the Peter Pans of the avian world". According to this theory, ratites evolved, not flightlessness, but a thyroid dysfunction!

Second, the out-of-Gondwana solution to Darwin's puzzle presented so confidently by Smithsonian is contradicted by numerous evolutionists. The report by Harshman and others says that, "Finally, this phylogeny demands fundamental reconsideration of proposals that relate ratite evolution to continental drift." Olson says,

Furthermore, Sibley and Ahlquist (1981, 1983) assumed that the ancestral ratites originated in Gondwanaland and could have dispersed between continents only when they were joined in the Mesozoic, this being one of their major points for calibrating the supposed DNA "molecular clock." But we now know that not only were volant [flying] paleognathous birds [birds with ratite-like palates] abundant and widespread in the Paleogene of North America and Europe, but also that at least one, Palaeotis, had achieved a ratite grade of morphology by the middle Eocene. Therefore, the ratites certainly cannot be regarded as having originated in Gondwanaland.

In sum, the field of ratite evolution is in utter turmoil. Oh, Smithsonian, has Darwin's concern truly been solved? No way! Why, then, have you misrepresented the true status of the problem?

The inherent contradictions found in the evidence, and the multiplicity of theories that have arisen, proclaim loudly that the whole idea of ratite evolution ought to be abandoned. By contrast, not one fact contradicts creation theory. Not one! I betcha if Darwin could have foreseen the labyrinth of convoluted and contradictory theories about ratite evolution that his theory would sire he would have torn up "The Origin's" manuscript.

1Olson, Storrs L. 1985, The Fossil Record of Birds, Smithsonian Digital Repository

2Neoteny and the thyroid in ratites, Reviews of Reproduction (1996) 1, 78-81

3Evolution of the avian sex chromosomes from an ancestral pair of autosomes, Proceedings of the National Academy of Sciences, Vol. 95, pp. 8147-8152, July 1998

4 Harshman, J. et. al. Phylogenetic Evidence for Multiple Losses of Flight in Ratite Birds", Proceedings of the National Academy of Sciences (USA), September 9, 2008, 105 (36): 13462-13467

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