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.
Seems to me that any Christian who would measure how much of a Christian another Christian is sincerely human. Although I do not doubt that Christ had risen, I do not see the evidence of this, don't need to, so it's not on the list. Many things on not on the list that could be.
What is stupid is to summarily dismiss that which we don't fully understand, be it scientific or spiritual.
I don't even count the 120 yrs as significant.
The whole outline of sequential appearance of life is unusual for bronze age writing, possibly unique.
I know that it is wrong in a lot of detail, but it is certainly closer to modern evolutionary theory than the pagan myth of Adam and Eve.
bah - lawyeristic semantics! not buying it ;)
You only have to add heat to raise it to the ignition temperature. For some combustionables, the ignition temperature is less than ambient and you need no "spark" to set it off. In a diesel engine, you increase pressure to build up temperature to the ignition temperature. In a gasoline engine, we "spark it" to get it (locally) to the ignition temperature.
The air seperated the firmament that was the seas from the firmament above. Pararphrasing, I'll dust the Bible off in a bit and read the passage. Firmament meant water. I have heard it said when the firmament above collasped, for lack of a btter word, the earth flooded.
well, the epicureans came up with a physical model of microscopic matter similar in suprising ways to basic molecular chemistry and physics, but I have no need to ascribe the results of their deductive reasoning to divine inspiration or extraterrestrial technology transfer
Earthly "gods"; money, sex, power.....
We don't dismiss the spiritual, we eliminate it from science since science cannot address spirituality.
LOL Twisting and turning on a burning spit does not get you away from the fact that origin of life is not contained in the ToE.
"without any sort of "instructions"
Obviously, life had some sort of instructions when first formed, but they have changed in multiple ways since then and produced a variety of new life forms through biological evolution.
Biologists didn't invent the evolutionary tree. They constructed it from mountains of data. That it is not correct in every detail in no way diminishes the truth of it. If you want to argue that a detail wrong diminishes the whole, then you need to discard the Bible.
I don't disagree at all with the thoughts and sentiments you just expressed.
if the religious would kindly cease attempting to call their faith a science, and our science a faith, we'd all get along much better.
Time to dust of the old proof.
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There is a lot of evidence for God, you just don't know what it is.
Faith founded on fact is stronger than a faith based on "the trees and mountains are beautiful". Instead of attacking biology and science, you should go take a good course in Theology.
"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."
...
"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."
Use a hammer and you can make it fit.
That is just a rationalization. If you do not fully understand the significance of Christ's Resurrection, your teaching in Christianity is sadly lacking. Your pastor should be horsewhipped. (not literally) ;-)
Are you really so ignorant of evolutionary theory to believe that we evolved from apes or are you just a troll injecting the rediculous into the argument for disruption's sake?
Newbie, before you call someone a "troll", you better look to see how long they've been on FR. I'll still be here long after you've been banned for your constant personal attacks.
Why don't you explain then where man evolved from? Or is the sum total of what you post consist of insults and bile? You better worry less about "trolls" (which, by the way your posts are far more troll-like) and worry more about your ill-mannered, rude behavior.
Ok, just go out and have a few beers and reconsider. LOL
Hmmm.... "What the heck does all that have to do with biological evolution of the whale?"
hehe Gotcha! Whooohooo
Just kidding. :-)
Amen. And if the scientific would kindly stop referring to the religious as superstitious and idiotic because of their faith that too would help.
Oh. Well, you get the idea from looking at the drawings of the functions. No matter how much you zoom in or out, the figure looks kind of the same. It's the same thing over and over on bigger and smaller scales, no limit.
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