Scientists find missing link between whale and its closest relative, the hippo

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.

I didn't say that. I said "the beginning" and that's what scripture says. To me, the "beginning" clearly means the time when something starts or begins.

That would be Day One, NO?

No, I mean the beginning of creation. He brought forth light, land and water, the heavens, animal life, man, then he rested.

I suppose your point is that man wasn't made on day one, so what says that man wasn't evolving in the meantime? I would point to what God said on day six. "Let us make man in our image, in our likeness, and let them rule over the fish of the sea and the birds of the air, over the livestock, over all the earth."

That obviously indicates that man was made separately.

No, that sounds like the arguments evolutionists make. "No one can disprove evolution, therefore creation is false."

But this is not what I, and others on this thread are saying about the theory of evolution. This is a mischaracterization. No one says "no one can disprove evolution." Scientific theories by definiton are designed to be testable. If a test proves the theory to be in error, the theory must be revised.

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.

This does not follow. One can have faith in the Creator and yet believe in the validity of science. You are setting up a false dichotomy.

You mat want to do some research on Super Nova 1987A (SN1987A). You seem truly curious and I think you would find this fascinating. Here are a couple of links (There are many more):

http://zebu.uoregon.edu/~soper/StarDeath/sn1987a.html

http://homepages.wmich.edu/~korista/supernova_agesize.html

Thanks for that Tolstoy quote...I'd not seen it before. It's perfectly apt and worth remembering. Clearly, it's best to hold ones opinions lightly, recognizing that any or all of them might need revising (or discarding) in the face of fresh evidence.

Thanks, too, of course, for the wealth of links and information you've been providing us.

It says that God created man on the sixth day. Therefore, man was created toward the end of the process. All of this is perfectly consistent with the idea that man is a product of evolution, the same as all the other species of life on earth.

Not if you take all of the scripture concerning the creation of man into account. It then becomes clear that man was created separately. That's what I believe, you're free to differ. See post 382.

re: Whatever you say, hon. )))

Hon? Childish. It's been fun watching the Descent of the Species. I'll see ya on the next "All About Eve" post from our Originator. Who knows, by then we might even have that new fly we've been promised.

Willful blindness is almost always an incurable malady.
Sigh. This trend seems to be growing. :-(

It often seems so, doggone it (so to speak).

Hey, any luck with Parmenides?

If man is a product of evolution, is he not "formed from the dust of the ground"? If God created the first life, either directly or indirectly through the creation of laws of nature that led to the formation of life through natural processes, did He not "breath into his nostrils the breath of life"? I was assuming a figurative reading of the Scripture and asserting that evolution is consistent with that figurative reading. If you want to assert that the Bible is literally true, then you have problems other than evolution. For example, why do you have no problem with the Biblical assertion that the earth is fixed and does not move? I have heard it argued that relativity says it's correct to view things from a reference frame in which the earth is stationary. However, it's equally correct to view things from a reference frame in which the earth moves. Why then is there no problem with relativity?

"This does not follow. One can have faith in the Creator and yet believe in the validity of science. You are setting up a false dichotomy."

It's not a false dichotomy. You are reading it wrong. I specifically said if the Lord exists (and he claims to be Creator) then he did not use entirely natural proceses, or by definition, He didn't create.

Then I said, if scripture can be proved inspired, that Macroevolution (at least on the scale that we talk about) is false. That's because scripture makes very specific claims.

I believe in the validity of science. I believe in the scientific method. But I don't believe that the scientists who have adopted evolution are correct. There is a portion of scientific thought (evolution) that is wrong. It wouldn't be the first time and it wouldn't be the last time.

So, a lion can inter-breed with a tiger, but not with a cheetah.

This brings up another interesting bit of biology: While common convention puts cheetahs in the "cat" family -- and they certainly do have a number of characteristics of the cat family -- they also are closer to canids in some way than cats. For example, they have non-retractable claws like dogs (and unlike cats), and some features of their skulls are quite "doggy". Native Africans often classified cheetahs as dogs rather than cats.

While none of this is conclusive by itself, I'd be interested to see what the DNA of cheetahs says about its phylogeny whenever the genome labs get around to sequencing it. I'd predict that cheetahs are on a clade which split earlier from the canid/felid branch than most other species in the same group.

(Background: Although people often think of "dogs and cats" as classic opposites, the "dog group" and the "cat group" are actually closest cousins to each other in the carnivore diversification radiation. So the cheetah may be a result of being closer to the ancestral dog/cat common ancestor than either of the more specialized groups of descendants. DNA analysis will be able to answer this for sure one way or the other.)

Agreed. I think it's wise to look to the Bible for moral guidance, but not for scientific information. I won't try to argue your views about the direct creation of man since I am sure there's no point in doing so. You believe what you belive as a matter of faith and there's no way any amount of logic, facts, or evidence will convince you otherwise. Like you, I don't see the findings of science as being particularly relevant in the spiritual realm, so I am not surprised that most of the findings of science are not mentioned in the Bible.

I have heard it argued that relativity says it's correct to view things from a reference frame in which the earth is stationary.

This is astronomer Tycho Brahe's diagram of a stationary (geocentric) earth with the sun going around daily. It first appeared in 1588.

Funny you should mention cheetah genetics. I was just reading about them:

The cheetah originated about 4,000,000 years ago, long before the other big cats. The oldest fossils place it in North America in what is now Texas, Nevada and Wyoming. It was common throughout Asia, Africa, Europe and North America until the end of the last Ice Age, about 10,000 years ago, when massive climatic changes caused large numbers of mammals to disappear. All cheetah in North America and Europe and most of those in Asia and Africa vanished. Some experts think our present populations were derived from inbreeding by those very few surviving and closely related animals. This inbreeding "bottleneck", as theorized, led to the present state of cheetah genetics: all cheetah alive today appear to be as closely related as identical twins.

Cheetah Spot

Not me, but the people who actually believe that a mammal went to the land, then went back to the water and develped some sort of mechanism to breath underwater or breach the water and breath air, they are the people who lost credibility.

...and since these "people" exist only in your own head...

"If you can prove the Lord, what do you need faith for?"

For those long times in between seeing proof when people are constantly telling you that He doesn't exist, or He said x when you know He said y, or when they claim that God is not trustworthy when you know He is.

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