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Scientists find missing link between whale and its closest relative, the hippo
UC Berkeley News ^ | 24 January 2005 | Robert Sanders, Media Relations

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.


TOPICS: Culture/Society; Miscellaneous; Philosophy
KEYWORDS: crevolist; darwin; evolution; whale
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To: balrog666

First I want to know about the badger-creature. He's holding out.


561 posted on 02/08/2005 2:17:23 PM PST by Mamzelle
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To: houeto
Because Junior called me a Holdenite. Ted Holden.

OH, that is where you had heard the name. Then why did you say you had not heard of him if you had heard from him via Junior?

562 posted on 02/08/2005 2:17:48 PM PST by WildTurkey (When will CBS Retract and Apologize?)
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To: Mamzelle
Is this on the level? I don't know what it is-- I am no zoologist, but it has the look of a swamp predator like a badger or something marsupial-- I wouldn't want to antagonize it

It's a type of cat called a bear-cat.

563 posted on 02/08/2005 2:18:04 PM PST by Modernman (What is moral is what you feel good after. - Ernest Hemingway)
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To: balrog666

It's a bird, or am I missing something?


564 posted on 02/08/2005 2:18:34 PM PST by Modernman (What is moral is what you feel good after. - Ernest Hemingway)
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To: Ichneumon

I'm finding that I'm bookmarking threads just to keep your links.


565 posted on 02/08/2005 2:19:44 PM PST by <1/1,000,000th%
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To: balrog666

Looks like some type of badger.


566 posted on 02/08/2005 2:19:50 PM PST by Modernman (What is moral is what you feel good after. - Ernest Hemingway)
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To: WildTurkey; Junior
He does know how to google.

That's what I told my dad. "Come on Pops, even idiots know how to google!"

567 posted on 02/08/2005 2:19:53 PM PST by houeto ("Mr. President , close our borders now!")
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To: SubSailor
You still haven't answered why you find it so compelling to convince people of your position. Why do you care so deeply about what other people choose to believe?

PMFJI, but why the heck are you on FreeRepublic???

568 posted on 02/08/2005 2:20:06 PM PST by jennyp (WHAT I'M READING NOW: Professional NT Services by Miller)
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To: SubSailor
You still haven't answered why you find it so compelling to convince people of your position.

You make the assumption that we are even trying to convince. We have no doubt that the radical creationists will never be convinced by scientific fact. That is why these thread degenerate.

569 posted on 02/08/2005 2:20:56 PM PST by WildTurkey (When will CBS Retract and Apologize?)
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To: Mamzelle

"Speciation is the question here--not that animals change."

There are hundreds of observed speciations.


570 posted on 02/08/2005 2:21:01 PM PST by shubi (Peace through superior firepower.)
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To: houeto
And upon what do you base that? The cisasteroidal worlds all have molten cores and they orbit the Sun rather nicely. One would think you could test for electromagnetic attraction between these worlds and the Sun, but there doesn't seem to be any of significance.

Or is the evidence being suppressed by a cabal of astrophysicists bent on misleading the entire world for some mysterious purpose?

571 posted on 02/08/2005 2:21:31 PM PST by Junior (FABRICATI DIEM, PVNC)
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To: WildTurkey
Then why did you say you had not heard of him if you had heard from him via Junior?

Hmmm...good question.

572 posted on 02/08/2005 2:22:09 PM PST by houeto ("Mr. President , close our borders now!")
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To: Liberal Classic

The never understand how populations differ from individuals. It is willful ignorance.


573 posted on 02/08/2005 2:22:18 PM PST by shubi (Peace through superior firepower.)
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To: Modernman
But where are the wheels?
574 posted on 02/08/2005 2:22:22 PM PST by Mamzelle
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To: SubSailor
You still haven't answered why you find it so compelling to convince people of your position.

And how many times have you posted that his links don't work when in fact they do?

575 posted on 02/08/2005 2:24:08 PM PST by WildTurkey (When will CBS Retract and Apologize?)
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To: balrog666

And the answer........Echidna........nearest relative you would say is the platypus, but I think it is his mother.


576 posted on 02/08/2005 2:24:40 PM PST by Texas Songwriter (p)
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To: shubi
The never understand how populations differ from individuals. It is willful ignorance.

I think it is seeing oneself as the center of the universe.

577 posted on 02/08/2005 2:25:20 PM PST by WildTurkey (When will CBS Retract and Apologize?)
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To: HankReardon

A coyote and wolf are two different species. They do not breed in the wild. You must differentiate between selective breeding and natural selection.

Don't get confused by Darwin's example of selective breeding in Origin of Species. He didn't mean to say it was identical.


578 posted on 02/08/2005 2:26:54 PM PST by shubi (Peace through superior firepower.)
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To: Texas Songwriter
And the answer........Echidna........nearest relative you would say is the platypus, but I think it is his mother.

And was that "kind" on the ark?

579 posted on 02/08/2005 2:27:52 PM PST by balrog666 (A myth by any other name is still inane.)
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To: Modernman
A mongoose that smells like Fritos
580 posted on 02/08/2005 2:27:57 PM PST by Mamzelle
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