Posted on 02/08/2005 3:50:43 AM PST by PatrickHenry
A group of four-footed mammals that flourished worldwide for 40 million years and then died out in the ice ages is the missing link between the whale and its not-so-obvious nearest relative, the hippopotamus.
The conclusion by University of California, Berkeley, post-doctoral fellow Jean-Renaud Boisserie and his French colleagues finally puts to rest the long-standing notion that the hippo is actually related to the pig or to its close relative, the South American peccary. In doing so, the finding reconciles the fossil record with the 20-year-old claim that molecular evidence points to the whale as the closest relative of the hippo.
"The problem with hippos is, if you look at the general shape of the animal it could be related to horses, as the ancient Greeks thought, or pigs, as modern scientists thought, while molecular phylogeny shows a close relationship with whales," said Boisserie. "But cetaceans – whales, porpoises and dolphins – don't look anything like hippos. There is a 40-million-year gap between fossils of early cetaceans and early hippos."
In a paper appearing this week in the Online Early Edition of the Proceedings of the National Academy of Sciences, Boisserie and colleagues Michel Brunet and Fabrice Lihoreau fill in this gap by proposing that whales and hippos had a common water-loving ancestor 50 to 60 million years ago that evolved and split into two groups: the early cetaceans, which eventually spurned land altogether and became totally aquatic; and a large and diverse group of four-legged beasts called anthracotheres. The pig-like anthracotheres, which blossomed over a 40-million-year period into at least 37 distinct genera on all continents except Oceania and South America, died out less than 2 and a half million years ago, leaving only one descendent: the hippopotamus.
This proposal places whales squarely within the large group of cloven-hoofed mammals (even-toed ungulates) known collectively as the Artiodactyla – the group that includes cows, pigs, sheep, antelopes, camels, giraffes and most of the large land animals. Rather than separating whales from the rest of the mammals, the new study supports a 1997 proposal to place the legless whales and dolphins together with the cloven-hoofed mammals in a group named Cetartiodactyla.
"Our study shows that these groups are not as unrelated as thought by morphologists," Boisserie said, referring to scientists who classify organisms based on their physical characteristics or morphology. "Cetaceans are artiodactyls, but very derived artiodactyls."
The origin of hippos has been debated vociferously for nearly 200 years, ever since the animals were rediscovered by pioneering French paleontologist Georges Cuvier and others. Their conclusion that hippos are closely related to pigs and peccaries was based primarily on their interpretation of the ridges on the molars of these species, Boisserie said.
"In this particular case, you can't really rely on the dentition, however," Boisserie said. "Teeth are the best preserved and most numerous fossils, and analysis of teeth is very important in paleontology, but they are subject to lots of environmental processes and can quickly adapt to the outside world. So, most characteristics are not dependable indications of relationships between major groups of mammals. Teeth are not as reliable as people thought."
As scientists found more fossils of early hippos and anthracotheres, a competing hypothesis roiled the waters: that hippos are descendents of the anthracotheres.
All this was thrown into disarray in 1985 when UC Berkeley's Vincent Sarich, a pioneer of the field of molecular evolution and now a professor emeritus of anthropology, analyzed blood proteins and saw a close relationship between hippos and whales. A subsequent analysis of mitochondrial, nuclear and ribosomal DNA only solidified this relationship.
Though most biologists now agree that whales and hippos are first cousins, they continue to clash over how whales and hippos are related, and where they belong within the even-toed ungulates, the artiodactyls. A major roadblock to linking whales with hippos was the lack of any fossils that appeared intermediate between the two. In fact, it was a bit embarrassing for paleontologists because the claimed link between the two would mean that one of the major radiations of mammals – the one that led to cetaceans, which represent the most successful re-adaptation to life in water – had an origin deeply nested within the artiodactyls, and that morphologists had failed to recognize it.
This new analysis finally brings the fossil evidence into accord with the molecular data, showing that whales and hippos indeed are one another's closest relatives.
"This work provides another important step for the reconciliation between molecular- and morphology-based phylogenies, and indicates new tracks for research on emergence of cetaceans," Boisserie said.
Boisserie became a hippo specialist while digging with Brunet for early human ancestors in the African republic of Chad. Most hominid fossils earlier than about 2 million years ago are found in association with hippo fossils, implying that they lived in the same biotopes and that hippos later became a source of food for our distant ancestors. Hippos first developed in Africa 16 million years ago and exploded in number around 8 million years ago, Boisserie said.
Now a post-doctoral fellow in the Human Evolution Research Center run by integrative biology professor Tim White at UC Berkeley, Boisserie decided to attempt a resolution of the conflict between the molecular data and the fossil record. New whale fossils discovered in Pakistan in 2001, some of which have limb characteristics similar to artiodactyls, drew a more certain link between whales and artiodactyls. Boisserie and his colleagues conducted a phylogenetic analysis of new and previous hippo, whale and anthracothere fossils and were able to argue persuasively that anthracotheres are the missing link between hippos and cetaceans.
While the common ancestor of cetaceans and anthracotheres probably wasn't fully aquatic, it likely lived around water, he said. And while many anthracotheres appear to have been adapted to life in water, all of the youngest fossils of anthracotheres, hippos and cetaceans are aquatic or semi-aquatic.
"Our study is the most complete to date, including lots of different taxa and a lot of new characteristics," Boisserie said. "Our results are very robust and a good alternative to our findings is still to be formulated."
Brunet is associated with the Laboratoire de Géobiologie, Biochronologie et Paléontologie Humaine at the Université de Poitiers and with the Collège de France in Paris. Lihoreau is a post-doctoral fellow in the Département de Paléontologie of the Université de N'Djaména in Chad.
The work was supported in part by the Mission Paléoanthropologique Franco-Tchadienne, which is co-directed by Brunet and Patrick Vignaud of the Université de Poitiers, and in part by funds to Boisserie from the Fondation Fyssen, the French Ministère des Affaires Etrangères and the National Science Foundation's Revealing Hominid Origins Initiative, which is co-directed by Tim White and Clark Howell of UC Berkeley.
Just one question: Are you truly under the impression that this is an accurate summary of that article, and the subsequent discussion? Because if so, you're vastly mistaken.
Or are you just lying about it?
Either way, your misrepresentation bears little resemblance to the reality.
Hmm, come to think of it, the same could be said for most of your posts on this thread.
After reading 350 of these threads, it appears to me that the word species is loosely-knit.
That's your characterization, not my translation, and a very telling one on your part, indeed.
So, you don't think that a scientist should be very careful to avoid those tricks of analysis that are just surface appeal? It has surface appeal that, if you cut off the tails of enough mommy mice, sooner or later the offspring will lack tails. It had enough appeal that it was an actual experiment. Tail-less mice didn't happen, but such assumptions frequently mislead.
Modernman suggested that weakening the species of dog through breeding (the papillion, an obviously weak little misbegotten creature) would lead to a new species. I assert that it merely would lead to a fetid gene pool and inevitable "extinction" of a breed type.
Surface appeal can mislead people testing a new drug--frankly, it misleads all the time. As I have said, the evo-priests would do well to read briefs written by pharmeceudical developers to know how scientists should write and think, which is cautious and qualified and respectful of the guinea-pig public. 'Cause if pharm guys get pompous, arrogant, grandiose and ego-addled, they'll kill somebody and land in jail. Evo-guys just get tenure, I suppose.
re: Your "leap" is still a huge one. Dogs are still dogs--goats are still goats. Humans are still primates... Still apes too, for that matter.
Here you rather worry me...I do hope that "canine" means more to you than "dog"-- dog is a subset of canine, as ape is a subset of primate. And PhD is a subset of Grantgrubbicus.
No one can disprove the Lord, therefore evolution is false? Hmm. :\
Creationists admit to speciation within kind. Man's demonstrated that with dogs, horses, pigs, cows, etc.
But just because a lion and a tiger can mate with mixed results, doesn't prove either that they were created separately or that they are an example of genetic sorting from a common ancestor. And even scripture doesn't help me out much there.
But to go from a hippo to a whale. That's just not believable.
Life is more like a spread spectrum. People like to put things into categories, though, so we have taxonomy.
No, that sounds like the arguments evolutionists make. "No one can disprove evolution, therefore creation is false."
But if you can prove the Lord, then evolution as purely the consequence of natural phenomenon is false. If you can prove the scripture is inspired, then macro-evolution is false.
Whatever you say, hon. You believe whatever helps you deal with those pesky "facts" thingies.
I don't know how life began, and I don't credit these erstwhile Darwin-thumpers who claim to know, either.
Obviously.
I have beliefs--but I don't call people "superstitious" or "ignorant" who don't happen to agree.
Neither do I. I call people ignorant when they *are* ignorant -- when they have little or no knowledge of a field, but insist on pontificating on it anyway and using their misconceptions (and often outright fantasies) in order to get snotty with people who *do* have such knowledge. When someone spews multiple inanities which are in direct opposition to the *facts*, they're being ignorant. And for some reason the more ignorant someone is on a particular topic, the more belligerently arrogant they seem to be about it -- perhaps as a defense mechanism. Instead, they would be well advised to have some humility -- especially when they have so *very* much to be humble about.
And, while you follow the article, follow the money. That's generally a good way to find a liar.
Sigh. This trend seems to be growing. :-(
When does this change stop? If it keeps going for lone enough...
But to go from a hippo to a whale. That's just not believable.
More believable than killing a thousand men with the jawbone of an ass?
Yes, I don't buy evolutionist's claim that "statistical improbability" is not a valid argument.
By the way, evolutionists argue from incredulity all the time when they say, "It must have been from natural causes, because a designer is unbelievable"
Not only scientifically illiterate, but just plain illiterate.
With this exception:
Gen: 2
[7] And the LORD God formed man of the dust of the ground, and breathed into his nostrils the breath of life; and man became a living soul.
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