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.
Why, do you really *enjoy* horse manure that much? And yes, I can document that assessment to any level of detail you'd like.
Let's look at one of the opening paragraphs, for example:
Yet the fossil has absolutely no connection with the whale. Its skeleton turned out to be a four-footed structure, similar to that of common wolves. It was found in a region full of iron ore, and containing fossils of such terrestrial creatures as snails, tortoises, and crocodiles. In other words, it was part of a land stratum, not an aquatic one.This is just.... moronic. Yes, "its skeleton turned out to be a four-footed structure" -- THAT'S THE FREAKING POINT. That in no way supports their opening claim that "the fossil has absolutely no connection with the whale", and only an idiot (or an anti-evolutionist propagandist, but I repeat myself) would think that it did.
Even more jaw-droppingly stupid is the next sentence: "It was found in a region full of iron ore," (um, yeah, so f***ing what?) "and containing fossils of such terrestrial creatures as snails, tortoises, and crocodiles. In other words, it was part of a land stratum, not an aquatic one."
EARTH TO IDIOTS: snails, tortoises, and especially CROCODILES are SEMI-AQUATIC, you MORONS. How many crocodiles have you seen living in terrain *NOT* on the shore of some river, lake, or ocean?
For pete's sake, just how STUPID are these people? Crocodiles et al live PARTLY IN THE WATER, PARTLY ON LAND -- and gosh, SO DID THE ANCESTRAL WHALE being discussed. So by what brain fart did these imbeciles manage to take the presence of *crocodiles* as somehow a "disproof" of the scenario that the ancestral whale found in the same spot had a similar way of life?
The mind *boggles* at the ability of the anti-creationists to MISS THE POINT so badly.
And how can you be so enamored with such nonsense as to call it "just awsome"? Most gradeschool kids could have made more sense than that web page.
And not just their "misinterpretation of Scripture" -- they work overtime at misrepresenting science as well.
Perhaps you should refrain from name-calling if you are truly a Bible believing Christian.
Apparently not, actually.
What species will human kind become? Evolution works both ways, don't just look to the past, look to the future. What will the squirrel become? What will the bald eagle become?
"I don't want to argue this at length. I don't subscribe to your idea and you don't subscribe to mine. We're even."
No we are not even. I am a biologist and you are not. I am a Biblical scholar and you are not.
Ping
Being a Biblical scholar, are there parts of the Bible you consider to be merely figurative?
But then you'd never come here to post, and we'd miss you...
LOL!!
You missedit again!!
For over a century, evolutionists have been tellng us that whales came from the ancestor of the hippo, now they are telling us that hippos came from the whales ancestor!
And what I said earlier is still valid, you guys must think people are stupid or something, but dont you dare call it science.
Oh yeah? Well ... you got no evidence!!!
</creationism mode>
If God has a hand in the affairs of men, then why is it so hard to believe that God also has a hand in the affairs of animals?
God is the creator and author of the universe. If, as the Bible says, God knows the number of hairs on a man's head, and that nary a bird can fall from the sky without His knowledge, then why can you not accept that God also might have a hand in forming the traits of animals over a long period of time?
Where does it say in the Bible that God created animals which will never change one little bit?
I am touched!
How will the environment in the future be different from what it is currently? In what ways are the current anatomy and physiology of humans, squirrels, etc. insufficient to deal with these future environmental changes? If there are no environmental changes that a species can't deal with, then there's no selection pressure and therefore no major changes to a species. If there is a selection pressure, then the nature of that pressure must be known in order to determine the result of evolution of that species.
What is really frustrating is their ability to attack science with no scientific evidence whatsoever.
Even Bible interpretations take more knowledge than the AIG or ICR attacks on science. It just illustrates the sad state of affairs in science education.
Yeah! What he said! And also, it takes one to know one!
I think he's objecting to your "dramatic change" phrasing. While the end result XX million years down the road may look "dramatically" different from its distant ancestor, the phrase "dramatic *change*" sounds too much like the folks who expect that if evolution were true it would have to work by at some point having "a fish give birth to an elephant" or somesuch.
The actual *change* at any given point (i.e. generation to generation) is actually not very "dramatic" at all. It's only in the long run that all the smaller changes accumulate to the point of something "dramatically" modified from where it may have started.
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