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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: HankReardon
I did not even imply that I might be better than a maple tree. I am just delighted to have discovered we are related!

Come on, you can't see that AlGore is the missing link?

541 posted on 02/08/2005 1:57:30 PM PST by Lazamataz (Proudly Posting Without Reading the Article Since 1999!)
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To: Modernman

OK. It's a radger. Or a baccoon. Knowing your fondness for muling around, I figure it's gotta be a combo.


542 posted on 02/08/2005 1:59:13 PM PST by Mamzelle
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To: Lazamataz
Come on, you can't see that AlGore is the missing link?

Between what and what?

543 posted on 02/08/2005 1:59:21 PM PST by Doctor Stochastic (Vegetabilisch = chaotisch is der Charakter der Modernen. - Friedrich Schlegel)
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To: houeto
Indeed, the Moon's core is not solid, and that is why it is tidally-locked. Good for you. However, your original statement:

The swinging weight of a molten moon core would either have sent the moon flinging off into space or would have sent it crashing to earth.

Is still not accurate. Several Jovian and Saturnian moons have molten cores (hence, vulcanism) and they have neither been sent "flinging off into space" or crashing into their primaries.

544 posted on 02/08/2005 1:59:53 PM PST by Junior (FABRICATI DIEM, PVNC)
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To: Modernman

Oh, and you won't. When you don't define your terms, they can mean anything.


545 posted on 02/08/2005 2:00:07 PM PST by WildHorseCrash
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To: houeto

Google the name. He's quite famous.


546 posted on 02/08/2005 2:01:44 PM PST by Junior (FABRICATI DIEM, PVNC)
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To: Mamzelle
Nope. It's not a hybrid. It's a stand-alone species.

What "kind" do you think it would fit into?

547 posted on 02/08/2005 2:02:45 PM PST by Modernman (What is moral is what you feel good after. - Ernest Hemingway)
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To: Junior
Indeed, the Moon's core is not solid, and that is why it is tidally-locked. Good for you. However, your original statement:

No. I think his original statement had something to do with he could not understand why the moon didn't spin and now he has cut and paste from the site that I paraphrased my response to him from. He does know how to google.

548 posted on 02/08/2005 2:04:37 PM PST by WildTurkey (When will CBS Retract and Apologize?)
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To: Modernman

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


549 posted on 02/08/2005 2:07:02 PM PST by Mamzelle
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To: Modernman
http://media.animal.discovery.com/fansites/petstar/videogallery/season3/ep309_winner.html

Which "kind" is this? What's his nearest cousin?

No cheating now!

550 posted on 02/08/2005 2:11:28 PM PST by balrog666 (A myth by any other name is still inane.)
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To: WildTurkey
What is your story. You who posts: BWAAA HAAA HAAA HAAAA!

I pointed out the irony of a pompous know-it-all insisting on people checking facts and referring to his posted list as his proof, when the first 2 links I clicked on in his list led to nowhere. Not only had the links expired, they have been expired for over 4 years. Also, I have made no attempt to convert anyone to any position in this thread, nor have I posted supposed facts supporting either position. Nor have I claimed to be polite. 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?

551 posted on 02/08/2005 2:11:36 PM PST by SubSailor
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To: Ichneumon

So you do believe that God created you. That is all I wanted to know.


552 posted on 02/08/2005 2:11:45 PM PST by Texas Songwriter (p)
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To: Mamzelle
There have been several observed speciations in Drosophila
553 posted on 02/08/2005 2:12:36 PM PST by shubi (Peace through superior firepower.)
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To: Junior
It would help immensely if creationists would actually search for the actual source of their quotes instead of lifting them verbatim from some creationist website.

Yes. I saw Gould quoted earlier and thought the same thing.

"Since we proposed punctuated equilibria to explain trends, it is infuriating to be quoted again and again by creationists -- whether through design or stupidity, I do not know -- as admitting that the fossil record includes no transitional forms. Transitional forms are generally lacking at the species level, but they are abundant between larger groups. Yet a pamphlet entitled 'Harvard Scientists Agree Evolution Is a Hoax' states: 'The facts of punctuated equilibrium which Gould and Eldredge...are forcing Darwinists to swallow fit the picture that Bryan insisted on, and which God has revealed to us in the Bible.'" -- Stephen Jay Gould

554 posted on 02/08/2005 2:12:56 PM PST by houeto ("Mr. President , close our borders now!")
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To: WildTurkey
If you have never heard of him, how did you know his name?

Because Junior called me a Holdenite. Ted Holden.

555 posted on 02/08/2005 2:14:16 PM PST by houeto ("Mr. President , close our borders now!")
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To: Modernman
That one was kind of difficult, so here's another.


Which "kind" is this? What's his nearest cousin?

No cheating now!

556 posted on 02/08/2005 2:15:33 PM PST by balrog666 (A myth by any other name is still inane.)
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To: SubSailor

So, you think I am haughty? Sniff...boohooohooo

LOL


557 posted on 02/08/2005 2:15:40 PM PST by shubi (Peace through superior firepower.)
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To: SubSailor
I pointed out the irony of a pompous know-it-all insisting on people checking facts and referring to his posted list as his proof, when the first 2 links I clicked on in his list led to nowhere.

As he said earlier, you had better check your computer or ISP. I just validated that his first three links and all those I checked (4) up to about #20 worked.

558 posted on 02/08/2005 2:16:12 PM PST by WildTurkey (When will CBS Retract and Apologize?)
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To: Jaysun

Who says you are simpler than a plant?


559 posted on 02/08/2005 2:16:39 PM PST by shubi (Peace through superior firepower.)
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To: Junior
Several Jovian and Saturnian moons have molten cores (hence, vulcanism) and they have neither been sent "flinging off into space" or crashing into their primaries.

That is why I think that an electromagnetic influence is underway. Gravity would not hold the moons in place.

560 posted on 02/08/2005 2:16:50 PM PST by houeto ("Mr. President , close our borders now!")
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