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.
LOL back to recess
And if you are not a creationist, why do you care if they have been debunked?
I just want reality accurately described by science. That's not too much to ask. Do you think the brontosaurus actually existed?
Behe is making $$ from fools that buy his DVD's ...
Ummmm... God created chimps in his image. Makes sense. I saw The Planet of the Apes.
That's telling us!! You think it's billions and billions of dollars like Carl Sagan wish he made?
Idiotic Website Creationist Alert.
You lack of understanding of biology and science
Seems your total education in science is a couple of visits to some frauds website. I just hope you didn't spend any money for his DVD's.
Boil a pot of gook and see what you come up with. There is a lot more than a source of heat required to create the complexities of life. This is not to say that the creation argument is the answer (I don't necessarilty think it is), it's just that your simpleton view of science is ridiculous and explains nothing.
Sort of like the trolls last fall.
It looks like you're going to make 2000 posts.
You got the best scientific answer to your question. For you to say we are idiots means that you have ZERO background in science.
But my point is... you are just as blind (or maybe naive is a better description) as the wacko fundamentalist to believe in a theory to the point where you follow it to its conclusion without the necessary scientific evidence.
Entropy is increased when you drive your car, but it gets you from point a to point b ...
Why would an "intelligent designer" make the same design error in only two lines of heredity and not in all of them?
In response you wrote:...man and chimp have much morphologically in common so if God designed there bodies to do similar things they'd have similar deficencies.
So the answer is, ultimately, because the Lord made them that way.
How do you argue with that?
Now, the existance of a Creator is not meant to be tested but should be considered culturally axiomatic...
I guess the answer is you don't argue with that.
What can and should be tested is any claim as to how the Creator did something.
And how does one go about formulating a test of disproving the Lord's methods? More importantly, and this is really what I'm trying to get at, how does creationism allow us to pose scientifically useful questions? How do we put forth questions which push the bounds of scientific understanding and technological know-how if the answer to every question is "Well that's the way the Good Lord made it?" How do we encourage curious exploration of the world around us when every question may lead us to heresy?
This is why I object to creationism being portrayed as a scientific theory of the same weight and usefulness as evolution. It is not science. It is not testable. It is not falsifiable. It makes no predictions, except that I am going to spend eternal torment in the place where the guy with the horns and the pointed stick conducts his business.
it isn't an hypothesis - it is a known set of facts.
any roughly spherical body eliptically orbiting a sun and revolving on an axis significantly other than paralell to the plane of the ecliptic, having an atmosphere and large bodies of water-based liquid, shall undergo the following:
1. diurnal cycle (day and night, the most obvious periodic cycle of radiation modulation)
2. cyclical aphelion and perihelion (farthest and closest to sun - yet more variation on the radiation levels on a cyclical basis)
3. coriolis effects in air motion and water-body current convection
(4. if the axis is neither perpendicular nor paralell to the ecliptic, the satellite shall also experience seasons)
((5. given the appropriate ambient temperature range, the satellite shall also experience localized incidence of evaporation, convection, condensation, and precipitation - rain, weather)
period. paragraph. RadioAstronomer and'or Dawsonville_Doc can easily confirm these details, and provide you with significant heaps of corroborative data.
these are forms of "order" or pattern imposed on the disorder-full "partial system"
I did not speculate on the effects this might have had on pre-living organic chemicals: radiation effects and complex chemistry are beyond my knowledge base. Had I done so, those speculations would have formed one or more hypotheses. Being largely ignorant of radiation-driven chemistry, I chose to keep silent on the topic.
I do know that radiant energy has significant effects on broad ranges of chemicals. RightWhale may well have input on that topic.
I suggest you look up entropy when you get a chance. You obviously do not have a degree in science. Entropy is NOT a catalyst for chemical reactions.
I suggest you look up entropy when you get a chance. You obviously do not have a degree in science. Entropy is NOT a catalyst for chemical reactions.
Next time, turn the light on in his head before handing it to him ...
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