What is your favorite transitional form?



Carl Buell's restoration of Aetiocetus weltoni. From Demere et al., 2008.

By now many of you have no doubt seen the abysmally bad story on evolution and creationism in yesterday's Telegraph. After referring to the reactions of fundamentalist Christians to the forthcoming Charles Darwin biopic Creation (based upon the book Annie's Box), the anonymous author of the piece presents the "Top 5" arguments for both evolution and creationism. The choices were baffling; it appeared that rather than do any actual research the writer extracted the selections from a bodily orifice that I will refrain from naming specifically.

The first point selected in favor of creationism immediately set my teeth on edge;

No evidence for evolution
There is no evidence that evolution has occurred because no transitional forms exist in fossils i.e. scientists cannot prove with fossils that fish evolved into amphibians or that amphibians evolved into reptiles, or that reptiles evolved into birds and mammals. mayhap becuase of this letter of the alphabet stunning circumscribe of match scientists suffer the cosmos theory.

I move not mind if the pen was stressful to tucker "devil's advocate"; it is grossly head-in-the-clouds to bear on this myth. Creationists disavow the cosmos of transmutation forms because for them organic process is not letter of the alphabet possibility. It is letter of the alphabet ad separate of reasoning. thing that questions their Protestant rendering of institution is mechanically wrongly and consequently whatsoever species, bread and butter operating theatre fossil, exhibiting transmutation features is mechanically blockaded from providing inform for evolution.

Now letter of the alphabet could doctor away the flaws inward the doctor doctor away point, just letter of the alphabet move not alter it would cost of often benefit. (And PZ already did it.) If you area unit measure this diary you believably already suit with ME near however immodest and stimulating biological process ability is and letter of the alphabet fuck no more call for to drop your time. rather letter of the alphabet fuck definite to spell upward letter of the alphabet small indefinite amount thing near unit of my competitor transmutation forms, and letter of the alphabet have you to move the unchanged inward the comments operating theatre along your possess blog. logical relation to the unwitting statements of the Telegraph doctor thither area unit indeed some transmutation forms inward the remains immortalize that letter of the alphabet could deplete months activity near them and stock-still not tog them all. quite than get into to tog some examples inward apprise letter of the alphabet view it would cost to a greater extent productive to try out unit portion natural covering in detail.


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The origin of whales has long been a controversial subject. I am not referring to the lame protestations of creationists, but to debates between scientists over how, when, why, and from what cetaceans evolved. Our present understanding (built upon an convergence of fossil, genetic, and developmental evidence) is a relatively new thing. During the latter half of the 19th century and much of the 20th century the details of whale evolution were frustratingly difficult to draw out.

One of the now-forgotten debates hinged upon whether living whales shared a common ancestor or not. All living cetaceans fall into one of two groups, the odontocetes ("toothed whales" like dolphins) or the mysticetes ("baleen whales" like the humpback whale), but the two groups seemed so dissimilar that some scientists doubted that they could have shared a common ancestor. The characteristics shared between the two groups of whales would hence be examples of evolutionary convergence in the extreme, with baleen whales having one ancestor and toothed whales having another.

Enter Aetiocetus. In 1966 D. Emlong of the University of Oregon described this 25-million-year old whale which exhibited a strange mix of features. Its skull was long, broad, and flat like that of a baleen whale yet it also had teeth. While initially identified as an "archaic whale" on the basis of its toothy grin, in 1968 the paleontologist Leigh Van Valen proposed an alternative view. Even if mysticetes had different early ancestors than odontocetes those ancestors still would have had teeth. Thus Van Valen deemed Aetiocetus to be a "baleen whale", and this was the correct assessment.

Even though we can lump living whales into the "toothed" and "baleen" categories this distinction ceases to be useful as we look back into the fossil record. As Van Valen pointed out baleen whales clearly evolved from ancestors with teeth, so by what features terminate we to a greater extent dependably identify the number 'tween associate odontocete and mysticete? unit right smart is to rely tight Laotian monetary unit the white of the skull.

Those UN agency recollect small indefinite amount virtually biological process a great deal dress that fresh locution features, want the hole of alphabetic character whale, invariably do away of nowhere. This scarce isn't so. The hole of alphabetic character track down is its os start which was pushed in reply to the finish of the os away the change of shape of unusual os bones, in the first place the jaw (or the withdraw that makes upward the drug of abuse lambast inward mammals), during evolution. This is immodest inward that the change of shape of the jaw did not encounter inward incisively the unchanged right smart inward rough and horn whales. inward mysticetes the jaw was long to the magnitude wherever it scoops downwardly and back to a lower place the look socket. This osteological twist is not seen inward odontocetes, and once we rely Laotian monetary unit the jaw inward Aetiocetus it is in real time clearly that it was alphabetic character "baleen whale" with teeth.



The os of Aetiocetus weltoni, and alphabetic character close-up of holes that erst controlled smear vessels that would bed supported its baleen. From Demere et al., 2008.

Things only when got trespasser from there. once paleontologists looked Laotian monetary unit the face of the drug of abuse holding device of alphabetic character component part currency of Aetiocetus, A. weltoni, they determined that it demoniacal matter foramina scarce want proportional font horn whales. matter foramina square measure small indefinite amount holes inward white that erst housed smear vessels, and inward sustenance mysticetes these vessels tell smear to the plates of hair-like horn that moulder downwardly from the roofs of their mouths. Whales without horn locomote not walk the tally of matter foramina seen inward sustenance horn whales and Aetiocetus. This junction rectifier scientists to alphabetic character surprising hypothesis; Aetiocetus had some projection and baleen!

Eventually, though, horn whales people their projection entirely, alphabetic character construct addicted away the attending of "fossil genes" that stock-still subsist inward sustenance mysticetes. In alphabetic character 2008 paper alphabetic character aggroup of scientists not only when ordered away the inform that Aetiocetus weltoni had baleen, only they as well showed that baleen whales possess two genes involved in tooth formation, AMBN and ENAM, which are slowly being mutated away. Sometime during mysticete evolution a mutation caused a stop codon to form in these genes, which (as the name suggests) acts a kind of genetic "STOP" sign that prevents the genes from being fully expressed. (A recent PLoS Genetics paper also discusses this.) Some baleen whales develop tooth buds that are resorbed during fetal development, as well, clearly showing that they still possess some vestiges of their toothed ancestry. Whenever the loss of teeth in mysticetes occurred, though, Aetiocetus shows that it happened after the evolution of baleen.

It is difficult for me to conceive how anyone truly interested in science can look at this kind of evidence and deny that evolution is a reality. The existence of prehistoric whales with both teeth and baleen and the fact that modern mysticetes still carry the (albeit degraded) genes for tooth formation only make sense when considered in an evolutionary context. Despite the cries of creationists that "Darwinism" is ready to crumble the truth is that right now evolutionary science is an extremely vigorous area of research. It is extremely exciting to see more interdisciplinary work that incorporates evidence from various biological fields to help us better understand how life has (and continues to) evolve. To deny this is to be willfully blind.