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.
That statement is a crock. And I don't even need to 'splain why.
Read post #61, the first post that I posted on the subject. Notice the words inside the parantheses. (Evolution of immune reactions, et al) This was an example of one of the links. So, I did provide him with an invalid link. Another example of inadequate research on your part.
Be honest. Here is the message which gives you a redirect to the search engine and then to the article. Note that the message indicates it may be the fault on their server.
Follow your own advice and notice the tree. They have a common ancestor near the base of the artiodactyls.
You keep forcing people to decide if you're an idiot or a liar. You can even confuse ME on this, but doing so doesn't help your credibility.
Note that you wouldn't have to do this if all the evidence weren't against what you have decided must be true. If there were a shred of evidence or logic to support you, you could do a much better job of appearing reasonable.
Nikola Tesla invented the AC motor and transformer, 3-phase electricity and the Tesla Coil. Tesla is now credited with inventing modern radio as well; the Supreme Court overturned Marconi's patent in 1943 in favor of Tesla. Ten years after patenting a successful method for producing alternating current, Nikola Tesla claimed the invention of an electrical generator that would not "consume any fuel." This invention has ben lost to the public. "I have harnessed the cosmic rays and caused them to operate a motive device." - Tesla.
Tesla's evidence supported his theory. He actually proved it in experiment. Big money would have none of this crap of 'free energy' for the public. He was ridiculed and shunned and died in misery.
"Aside from the advances that we've made, man is the only creature that has a God conscience or religious nature."
Where is the conscience of creationists when they attack evolution with no facts? Where is their conscience when they offer no science to refute evolution, yet claim their view superior?
Where is the conscience of creationists when they alter scientists quotes?
Where is the conscience of creationists when they preach cultish heresy and conflate the Gospel and Genesis as needed for salvation?
I wouldn't put much stock in the conscience idea if I were you.
Sorry. I missed that since you placed it with "ideas" instead of the proper place with "links". That's whats happens when you throw big BWAAA HAAA HAAA HAAAA! into your post. That is why you probably missed it in your proofreading.
That's okay, I wasn't reeealy sorry.;o)
Probably the same place it is when they alter our posts. Had another creationist excuse bearing false witness because he was a soldier of God.
It gets worse all the time. And to imagine they let these guys own computers ...
"Tesla's evidence supported his theory. He actually proved it in experiment. Big money would have none of this crap of 'free energy' for the public. He was ridiculed and shunned and died in misery."
God will court martial that soldier. ;-)
Tesla lived a life of ease and relative luxury from the proceeds of his various patents. He spent his last years living in a NYC luxury hotel and spending his time going to parties and charity events in that city. He was not shunned nor did he die in misery.
You know, a simple search of Wikipedia would have helped.
That was what houeto meant. The government confiscated his free-energy machine because of Bush's family ties to big oil.
Considering he shuffled off this (Tesla) coil in 1943, the government must've used one of his inventions to divine the future...
To jump you ahead, houeto said science could not explain why the moon did not rotate. He was quickly informed that it did rotate once per revolution and he then said that was statistically improbable .... now he is onto the Tesla free-energy machine that the government or someone would have no part of since we could not allow the public to have free energy.
Who's upset?
Where? I don't see any pictures or drawings where the two branches meet?
Perhaps it's one of the following artiodactyls? Maybe it's the pig? or the Mouse deer?
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