Science Sites Stretch Truth About Transitional Form
A tiny piece of cartilage-turned-bone has science news sites jumping for joy about an evolutionary transitional form. But is it one? A closer look shows a much more complex picture than the simple evolutionary victory being told in the media.
“Long-sought fossil mammal with transitional middle ear found,” trumpeted PhysOrg; in close harmony, Science Daily sang about the “Long-Sought Fossil Mammal With Transitional Middle Ear.” Jennifer Walsh at Live Science was astonished at the “Jaw-Dropping Find: Ancient Mammal’s Ear Bones.” And New Scientist told its readers, with no shadow of turning, that “The bones of your middle ear were once part of a mammalian ancestor’s jaw. Now a remarkable Cretaceous fossil provides a snapshot of how this shift took place.”
What’s all the commotion about? A well-preserved specimen of Liaconodon, though crushed, was discovered in China.
Unfortunately, the fossil, while certainly interesting, does not paint so clear a picture of evolution. In their paper in Nature,1 Meng et al defended their interpretation that the bone represents an evolutionary transitional form, but Ann Weil, commenting in the same issue,2 brought out some problems: namely, convergence of multiple lineages, and possible evolutionary reversals. Animals living and extinct share some of the features of Liaoconodon but are widely separated on Meng et al’s phylogenetic diagram. In addition, the ossified Meckel’s cartilage (OMC) is resorbed or retained in development of some animals.
The confusing palette of traits in fossil and extant animal jaw bones and middle ears defies a simplistic explanation that the complex middle ear bones developed from mutations in ancient jaw bones (see 03/19/2007). The critical trait scrutinized in Liaoconodon is only a spur of bone attached to the ossicles, which were already advanced structures for hearing in this extinct mammal. (In living mammals, the ossicles are completely separated from the jaw.) It’s not clear what a small spur of bone would do to help or hurt hearing anyway. Ossicles are only transmitters of vibrations; the real hearing is done by the cochlea, auditory nerve and hearing center in the brain.
Weil was much more tentative than the news reporters who made it sound all but proven that ears evolved from jaw bones because of this “transitional” form. She said, “Their attachment in Liaoconodon might support the contention that the ear bones remained tenuously attached to the jaw higher in the evolutionary tree of mammals than some have supposed.” In other words, Liaoconodon is a high mammal already. And contention it is, because Weil admitted that “How, when and how many times these ossicles detached from the mandible during the course of mammalian evolution is a topic of some controversy.”
Whether or not some extinct mammals had bony attachments from their ossicles to the jaw says little about the function of hearing, to say nothing of its evolution.
1. Meng et al, “Transitional mammalian middle ear from a new Cretaceous Jehol eutriconodont,” Nature 472 (14 April 2011), pp. 181�185, doi:10.1038/nature09921.
2. Anne Weil, “Mammalian evolution: A jaw-dropping ear,” Nature 472 (14 April 2011), pp. 174�176, doi:10.1038/472174a.
News media are shameless in their promotion of Darwin. New Scientist genuflected with this ending quote: “‘Charles Darwin predicted animals like this would have existed,’ says Rob Asher of the University of Cambridge. ‘Palaeontologists have hypothesised [about it] for a long time – now we have a very well-preserved specimen.’” You can tell a secular science news reporter is lying: when Darwin is found in a sentence.
This is just another case of the truth-stretching, connect-the-dots, Charlie-worshiping gamesmanship we saw four years ago with Yanoconodon (03/19/2007). Read that commentary again; it still applies. Darwinians have much more to worry about than a tiny piece of ossified cartilage in an extinct animal; see 03/24/2011, 03/04/2011, 01/31/2011, 11/29/2010 (note links in commentary), and 270 other chain links on mammals going back 10 years.