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.
"However, can you not admire their determination to enter the lion's den, so to speak?"
No. Do you admire the person that goes into a marked minefield and gets blown up?
sad but true.
"we will never find common ground and will remain at odds with each other."
I don't want to find common ground with people that are detached from reality.
If it was in an effort to save someone else, then yes.
s-No. Do you admire the person that goes into a marked minefield and gets blown up?
sub If it was in an effort to save someone else, then yes.
It is a false effort to save someone on the creationist's part. They are saving them with a false Gospel.
It is like someone going into the minefield to rescue someone, handing them a grenade with the pin out and
waiting to blow up together.
sub If it was in an effort to save someone else, then yes.
It is a false effort to save someone on the creationist's part. They are saving them with a false Gospel.
It is like someone going into the minefield to rescue someone, handing them a grenade with the pin out and waiting to blow up together.?
I stand by my original statement. If I perceived that you were in danger, regardless of the correctness of my perception, then I think I should at least attempt to save you.
"I am right and you are wrong, I pity you, and remember I am a minister."
Obviously, you are very pertinacious. Apparently, from the past several discourses we have had, and taking into account the above statements, I have little chance of making any headway in affecting your resoluteness or your opinions.
I have enjoyed the opportunity to discuss these matters with you. I wish that we could agree more, but that does not seem likely at this time. Perhaps we shall meet again in some other thread, or in some other form. Good luck to you and I bid you peace.
placemarker
Come on. We all know what ID is. It is the NEW movement by radical fundamentalists to descredit evolutionary theory. They throw up a bunch of websites then they come here and quote those websites.
Just like Soros tried with drug legalization. Fill the webhits with false propaganda.
Now when a "student" goes to look up the second law of thermodynamics, he gets more hits on false science propaganda by the ID crowd than credible informative sites.
No. Since ID is based on the supernatural all powerful God who can do anything.
Yes they do argue to deceive. That is their only hope of hurting evolutionary theory.
The sun is a main sequence star. From the billions of examples of these stars we can see that the sun will get hotter and bigger as it ages. In 1/2 billion years it will be too hot here on earth. Eventually the sun will become so large that it will fill the sky and it will eat both Mercury and Venus, and maybe earth, too.
This should not be a revelation. The idea that the sun will burn out in 5 billion years is common enough, but that earth will be too hot long before then is probably not as commonly known.
That sentence was a joke I put in so people would do exactly what you just did. LOL
When a figure skater pulls a "hand" in, the hand does not speed up. It maintains its momentum/speed but since it is in a closer orbit, its Tau decreases. Your anology makes it easy to remember but is not technically correct.
For example, if an object is in a circular orbit at 1000 miles it will have a Velocity of V1000 and if you suddenly "push" it to a lower orbit it will still have a V1000 which is now too low to counteract centripetal acceleration causing it to fall closer to earth resulting in an elliptical orbit. To regain the circular orbit, you have to provide another boost at the correct time.
No, the IDers are mainstream people.
Now when a "student" goes to look up the second law of thermodynamics,
ID doesn't use the Second Law of Thermodynamics as an objection to evolution.
Actually, I'm not even sure you can say ID objects to evolution. My view is that what it objects to is an undirected explanation of biodiversity.
Here is a very recent article by Dembski which specifically addresses the issue.
From you link YEC's should consider ID their friend and join them in the destruction of Darwinism. No go back to DU.
Those Darwinists? I don't think so.
It ate Mercury in that simulation, but spared Venus, sort of.
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