Network News

X My Profile
View More Activity

How Whales Lost Their Legs

I'm starting to think this whole "Evolution" thing -- all that Darwin stuff -- may actually be true.

Here's an excerpt from a press release from Eurekalert about how whales started out as doggy-like critters on land and somehow wound up in the sea without any legs. But it took 15 million years to happen. You don't pull a stunt like that overnight.

Note the mention of the gene called Sonic Hedgehog. More genes need names like that.

"More than 50 million years ago the ancestors of whales and dolphins were four-footed land animals, not unlike large dogs....

"In findings to be published this week in the Proceedings of the National Academy of Sciences, scientists say the gradual shrinkage of the whales' hind limbs over 15 million years was the result of slowly accumulated genetic changes that influenced the size of the limbs and that these changes happened sometime late in development, during the fetal period.

"However, the actual loss of the hind limb occurred much further along in the evolutionary process, when a drastic change occurred to inactivate a gene essential for limb development. This gene - called Sonic hedgehog - functions during the first quarter of gestation in the embryonic period of the animals' development, before the fetal period.

"In all limbed vertebrates, Sonic hedgehog is required for normal limbs to develop beyond the knee and elbow joints. Because ancient whales' hind limbs remained perfectly formed all the way to the toes even as they became smaller suggests that Sonic hedgehog was still functioning to pattern the limb skeleton.

"The new research shows that, near the end of 15 million years, with the hind limbs of ancient whales nonfunctional and all but gone, lack of Sonic hedgehog clearly comes into play. While the animals still may have developed embryonic hind limb buds, as happens in today's spotted dolphins, they didn't have the Sonic hedgehog required to grow a complete or even partial limb, although it is active elsewhere in the embryo.

"The team also showed why Sonic hedgehog became inactive and all traces of hind limbs vanished at the end of this stage of whale evolution, said Cohn. A gene called Hand2, which normally functions as a switch to turn on Sonic hedgehog, was shown to be inactive in the hind limb buds of dolphins. Without it, limb development grinds to a halt...

"Researchers say the findings tend to support traditional evolutionary theory, a la Charles Darwin, that says minor changes over vast expanses of time add up to big changes."

[BOODLE UPDATE: This morning there was some discussion about progressivity in evolution, or the lack thereof. Dreamer posted a quote from Michael Shermer, the noted skeptic, shooting down the notion of progressivity:

"... the bias of progressive evolution can be seen in the grand description of life's history from bacteria to brains. Wipe out all forms of big and complex life today through a catastrophic meteor impact or nuclear war and, the progressive bias dictates, in a couple of billion years the surviving bacteria living in rocks deep beneath the earth's surface will emerge and reevolve into something like us again. The myth buster here is Stephen Jay Gould, the late Harvard paleontologist whose numerous books and popular essays on evolution have consistently chipped away at the belief in inherent evolutionary progress, proposing in its stead a theory of evolution that says we are nothing more than a glorious accident, a contingent quirk on life's landscape."

Achenbach then lamely weighed in with his own quarter-baked notion:

"I increasingly believe [why does that phrase suddenly strike me as pretentious?] that Gould overstated his case. Gould's book "Wonderful Life" sets out his vision of myriad contingencies in evolution that defy any "progressive" trend. He based that on the Burgess Shale, which shows all manner of body types in existence roughly 500 million years ago, almost all of which disappeared. His argument is that there was nothing superior about the surviving body plans; that it was just a lottery. And he is certainly right that, in any given mutation, there's no deterministic force, no natural progression toward something better. But I'd defer to Robert Wright [author of "Non-Zero"] on the broader issue of progressiveness in biology and in the universe on the whole."

A phone call to Robert Wright has yielded, via email, the following summary of what was wrong with Gould's argument:

"Gould acted as if the big question was whether the evolution of particular *species* was inevitable (or at least highly likely), when in fact no sensible person had ever argued that this was the case. Obviously, some cataclysm a few million years ago could have wiped out the primate lineage that evolved into humans. The big question, which Gould tended to obscure, is whether certain *properties* were very likely to evolve. E.g., if humans had been wiped out early on, would some other species eventually have evolved that had roughly a human level of intelligence? I think probably so, and many first-rate biologists do as well (e.g. Ed Wilson, the late William Hamilton)."]

[Meanwhile, this morning we get word of upcoming "3rd annual Conference on Precession and Ancient Knowledge" (CPAK), at the University of California at Irvine. It's all about ancient civilizations, which supposedly were a lot more sophisticated than most of us think. The conference will explore the issue of whether "celestial motion might play a role in the rise and fall of civilization." I have no idea what that means. But as I read this press release I hear the high-pitched cicada-like sound of worldviews crashing and a New Paradigm emerging.

"Speakers at this year's event include explorer Graham Hancock, author of Fingerprints of the Gods, archaeoastronomer Walter Cruttenden, author of Lost Star of Myth and Time, Mayan scholar John Major Jenkins, author of Maya Cosmogenisis 2012, rebel Egyptologist John Anthony West, author of Serpent in the Sky, and megalithic investigator John Burke, author of Seed of Knowledge, Stone of Plenty."

Someone needs to write a book with a title like Secrets of the Lost Sky Gods. And I need to get a new career in which I can be called an "archaeoastronomer" or, better yet, a "rebel Egyptologist."]

[Via yellojkt, here's a press release that says that whales are related to hippos.]

By Joel Achenbach  |  May 24, 2006; 6:37 AM ET
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   StumbleUpon   Technorati   Google Buzz   Previous: Enough About Me, What Do YOU Think of My Blog?
Next: The Moaning Paper and Cheney's Penknife

No comments have been posted to this entry.

The comments to this entry are closed.

RSS Feed
Subscribe to The Post

© 2010 The Washington Post Company