by Greg Mayer
Snakes are not the only tetrapods (or even lizards) to have lost their legs. Whales have lost their hind legs (the front ones are now their flippers), and we have a pretty good fossil record of how they did so, thanks in large part to the work of Phil Gingerich of the University of Michigan Museum of Paleontology (see his great whale evolution site here) and his collaborators.
Although whales lack external hind legs (except as rare teratologies), they do have internal rudiments of the hind limbs and pelvic girdle, as I was reminded during a recent visit to my and Jerry’s alma mater, the Museum of Comparative Zoology, where one of the Museum’s killer whale skeletons now hangs in the building across a new courtyard: note the remnant hind limb girdle at lower left.
Here’s a closer view.
In addition to the killer whale skeleton, there’s also a bottlenose whale skeleton; here’s its remnant hind limb girdle.
Both whales were hung in this new building (which is where the MCZ parking lot was in my and Jerry’s days) at the initiative of the MCZ’s director, Jim Hanken. The figure below, from Phil Gingerich, shows some of the fossil whales through which limb loss has been traced.
Here’s his caption for the figure (go to his website for full citations to the papers mentioned):
Figure 1. Skeletons of the archaeocetes Dorudon atrox and Rodhocetus balochistanensis compared to that of Elomeryx armatus, which is here taken as a model for the extinct group of artiodactyls (Anthracotheriidae, s.l.) that we now think may have given rise to archaic whales. Pakicetus has a distinctive skull and lower jaw, but is not demonstrably different from early protocetids postcranially. Note changes in body proportions and elongation of feet for foot-powered swimming in Rodhocetus, then later reduction of the hind limbs and feet as the tail-powered swimming of modern cetaceans evolved in Dorudon.
A. Elomeryx drawing from W. B. Scott, first published in 1894. B. Pakicetus skull from Gingerich et al. (1983). Terrestrial interpretation is pure speculation: what little is known of the skeleton resembles Rodhocetus. C. Rodhocetus skeletal reconstruction from Gingerich et al. (2001). D. Dorudon skeletal reconstruction from Gingerich and Uhen (1996). Figure may be reproduced for non-profit educational use.
I showed photos of the hind limb remnants of Maiacetus, Basilosaurus, and Dorudon skeletons at the USNM in an earlier post.
(Thanks to Jon Losos for checking whale ID’s for me.)
Creationists say that the vestigial hind limbs of whales are not vestigial at all – they’re useful in copulation (*I* realize that vestigial does not mean useless). Looking at the skeletons, it’s hard to imagine how they could be useful.
Which makes me wonder how they creationally, creatively rationalize the recurrent laryngeal nerve.
They do it by declaring their gods to be bumbling incompetents that can’t design their ways out of paper hats — though, of course, not in so many words.
No, really. They do.
Read it for yourself.
Cheers,
b&
Here is one way, they claim it is not poor design:
http://www.icr.org/article/recurrent-laryngeal-nerve-not-evidence/
Worse than simply claiming it’s not poor design, they say that this all-powerful god of theirs is constrained by all the rest of the bad design choices it was faced with. And they wrap it all in language of “Poor us! We’re not worthy, for we’re too blithering fucking stupid to imagine how it could possibly be less fucked up.”
Cheers,
b&
How in heck can they look at a walking catfish and not believe in evolution? That’s pretty much a rhetorical question.
Sorry, different link to the same article as Ben Goren.
Useful in copulation? Really?
Can I get a pair on Amazon? Srsly, anything that useful should have a market, don’t you think?
Maybe they come in XL …
I believe Mr. Gingerich was actually the first to suggest that Dorudon’s legs were not vestigial and useful in grasping it’s partner during copulation. I do not think this is originally a creationists idea.
Is there an explanation for why some whales got so big? And can it be traced in the fossil record?
Just you try to get your mouth around a blue whale.
A 40-foot, 30-ton grey whale is immune to predation by killer whales. A 15-foot, 2/3 ton grey whale calf is not.
If you compare Pakicetus to Rodhocetus to Dorudon to Basilosaurus, there’s a clear upwards trend in size, but there are also small cetaceans, like dolphins and porpoises.
Maybe they got smaller after the order as a whole became more aquatically adapted, as a means of filling a diet niche. I don’t know what the state of knowledge there is.
I thought it was because baleen whales like the “blue whales swallow almost 2,000,000kJ (almost 480,000kcalories) in a mouthful of krill, and take in 90 times as much energy as they burn during a single dive“. They are hugely [sic!] efficient feeders, but presumably that efficiency should go sharply down for smaller individuals.
I’m planning on going out to see the exhibit – and am working on getting Dr. Gingerich to come out to an Ann Arbor Science & Skeptics meet-up.
It’s pretty amazing how much information we have on whale evolution.
I vaguely recall that mutations in a single gene led to loss of legs in whales. Anyone know anything about that?
I haven’t heard this, and it doesn’t seem likely, given the long history of reduction. It’s not quite impossible though. One could imagine a series of mutations at the same locus, each one making the leg a bit smaller, occurring over a long time. But it couldn’t be a single mutation at a single locus.
GCM
According to an article by # Lars Bejder & Brian Hall from Evo Devo in 2002 4(6):445-58 –
“An evolutionary change in Hox gene expression—as occurs in snakes—or in Hox gene regulation—as occurs in some limb-less mutants—is unlikely to have initiated loss of the hindlimbs in cetaceans. Selective pressures acting on a wide range of developmental processes and adult traits other than the limbs are likely to have driven the loss of hindlimbs in whales.”
http://onlinelibrary.wiley.com/doi/10.1046/j.1525-142X.2002.02033.x/abstract
Interestingly this article
http://www.springerlink.com/content/q122m4p071p0j03t/
used the molecular ‘footprint’ of homeobox gene Hoxa-13 (! sorry – I am a non-geneticist!) to predict where limb loss might occur. Connecting to Jerry’s frog teeth ‘re-evolving’ they mention in the abstract the difficulties of doing this for “lizards, which, as a group, have a history of limb loss and limb re-evolution” which is fascinating!
Is that a very large window or a very small killer whale?
It’s a very large window. The whale is big, but not enormous– maybe 15 or 20 feet.
GCM
An offtopic question about fossils. Sometimes the fossils are “crushed” in 2D with minimal depth (like the snake fossil). Even bigger animals like ichthyosaurs are in this 2D form in the AMNH. And then sometimes you have 3D displays such as the whale here (or even normal sized animals such as horses and ground sloths at AMNH).
How do 3D fossils of normal sized animals form? i.le how come they arent crushed?
I don’t think this particular skeleton is a fossil. If such utterly perfect fossil skeletons were found, I think scientists would eat their boots in shock 🙂
Doesn’t it depend on the conditions in which the fossil formed – sank to the bottom of a muddy lake, washed down a river & deposited, etc & the later layering of rocks above?
Here’s a site aimed children -http://www.enchantedlearning.com/subjects/dinosaurs/dinofossils/Fossilhow.html
or a bit more wordy –
http://www.fossilmuseum.net/fossilrecord/fossilization/fossilization.htm
You can tell I work in a library!
More complete skeletons of Pakicetus were decribed in 2001 and do a much better job showing hindlimb evolution than the question mark skeleton in your figure.
J. G. M. Thewissen, E. M. Williams, L. J. Roe and S. T. Hussain, Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls, Nature vol 413, pages 277–281, 2001.
I love its question mark skeleton! Watch this space I suppose…
Carl Zimmer has a fascinating description of what is known about whale evolution in his book The Water’s Edge, stemming from a series of great discoveries over a period of years. Gingerich and Thewissen figure prominently.
The vestigial limbs of whales were actually one of the things that bothered me the most back when I was still a Creationist.
Bah! God gave whales legs so they could walk up the ramp to board Noah’s Ark.
Your research is quite incredible, wow!
After participating in actual dinosaur digs, it makes it rather hard to believe the Creationist theory. I believe that the arguments are more based on semantics. Those who hold to those beliefs really prefer the profound and the mystical, rather than hard facts. Evolution does not discount creationism, it just adds time to it.
Many years ago, I sat in a Rabbi’s class about the Bible. At that time his response was that a bunch of men got together and had to come up with an idea of how the earth was formed. Having no computers, or research tools or documents from ages past, they just sat down and worked out the idea that the earth was created in six days and man rested on the seventh. The last day was put in to get their flock to church!
Since that time, Christians have taken the Bible for its word as their own, even though it is the history of the Jewish people. And then they have altered it, taken out definitions and inserted words hundreds of years later to support their claims. The silly thing is that those claims are all based on opinion.
It may seem that I go around the bend on this comment. But the study of time does not make men less spiritual, but more profound as to how things came to be. The information is fascinating and compelling.
What I find silly is that these creatures are so very large and with quite large brains. Man in his own arrogant ways has placed himself at the top of intelligence, when whales circumnavigate the continent, communicate effectively and, silly as it sounds, it’s own feces kick starts the marine food chain.
Life amazes me. Thanks again for the great info.
The cetacean pelvis is important for copulation, defecation, and locomotion.
http://www.lamaq.ufsc.br/Artigos%20Aqu%E1ticos/Simoes-lopes,%202004.pdf
http://www.jstage.jst.go.jp/article/jvms/66/7/761/_pdf
The problem with calling something vestigial is that it doesn’t distinguish between a reduced function and a specialized function.
If you call the pelvis vestigial, you should call the forelimbs vestigial. They do not serve the same purpose as in land mammals, but they do serve a specialized purpose for marine living.
If whales had a pelvis like land mammals with bones that connected each side, they would be at a disadvantage. It would be too big of a solid mass and would hinder their swimming motion. It would also hinder the size of their offspring, since mammals give birth through the pelvis – and it is very important for cetaceans to have offspring that are large at birth and ready to go. They wouldn’t survive otherwise.
Aaron –
I realize that this comment is quite old, but if you happen to show up here again, any chance you can update the links? These didn’t work for me, and Google has not been helpful in locating peer-reviewed articles on the whale pelvis being involved in reproduction, etc.
Thanks!