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.
Easily explained:
The Moon rotates in the same direction as it revolves, and it is gravitationally locked into a 1:1 synchronization because the the formerly molten rock have cooled and solidified, and the resulting shape is permamently oriented with its major axis pointing toward the earth. This type of gravitational synchronization is fairly common in the solar system, almost always with a ratio of 1:1.
Now be a good guy and find out how many planets exhibit similar rotations.
Someone pinged me awhile ago and informed me that I may not have understood your post. I could only smile then.
I don't care what you might personally find "believable" or not -- the evidence overwhelmingly indicates that it did indeed happen, so either you need to learn about the evidence and see for yourself, or continue to sit there in the corner mumbling, "I don't believe it, I don't believe it, I don't believe it..."
"...The liger example shows, IMO, that speciation is a gradual process with lots of gray areas. As species drift further apart, such as house cats and lions, it becomes clear that they are distinct. However, some species are still close enough that thay can interbreed."
Exactly.
Since the beginning is "Day One" then the later passages are in error or Genesis is in error or you cannot literally interpret Genesis or other parts of the Bible.
I don't know a *single* evolutionist who makes that argument -- or *would* make such a moronic argument.
If someone says something that you *think* is that, then you weren't listening closely enough.
"I built that bridge, but do they call me Ian the bridgemaker? No. I built that church, but do they call me Ian the churchbuilder? No. But screw one sheep ..."
I've read it, which is how I know that you've grossly misrepresented both the paper, and the subsequent discussion.
I don't know whether you've done so out of confusion, or dishonesty, but neither option inspires confidence.
Why do Scotsmen wear kilts?
Because a sheep can hear a zipper being lowered at 500 feet.
Sure it's a valid argument. Now show us your math, which accurately models biological processes. We'll wait.
What's that? You say you *don't* have any actual statistical calculations based on valid models, nor do you know how such a calculation would be performed, you just don't "feel" like such a thing would be likely enough to actually happen?
(Feel free to prove me wrong... But until then, I call BS...)
By the way, evolutionists argue from incredulity all the time when they say, "It must have been from natural causes, because a designer is unbelievable"
I call BS *again* on you. Provide a cite to *any* evolutionist who has actually argued such an idiotic point in that way -- or retract your bogus accusation.
I'm getting *really* tired of the unsupported accusations from you folks. Put up or shut up.
The odds of this occurrence are infinitesimal.
I predict they will do neither. It's creationism, y'know.
Why would whales need to be on the Ark?
Actually, they're not. The Moon is tidally-locked to the Earth. A number of other satellites in the Solar System are also tidally-locked to their primaries.
No. They are predicted by scientific theory and the conservation of angular momentum. In fact, in billions of years from now, people on the moon will only see one side of the earth!
Hon? Childish. It's been fun watching the Descent of the Species.
Oh NO you don't... Don't you *DARE* try to pull that horsecrap...
You know, the "we anti-evolutionists are so genteel and refined, while those evolutionists are childish, name-calling brutes..." horsecrap.
I don't think anyone needs to be reminded that YOUR VERY FIRST POST on this thread was a snarky, *CHILDISH* remark on the article which started the thread, wherein you dismissively called evolutionary biologists "Evo-shamans" in search of a "juicy little grant for the seekers of PhD Welfare".
Your *second* post childishly asked, "Does this make you pope, or something?" and spoke of "no religious fanatic so obnoxious as the doctrinaire PhD crank longing for tenure and relevance".
Your *third* post sarcastically called me "so pious [...] So righteous! Righteous me a Grant!" and suggested "an altar to Hopeless Tenure Track and Our Lady of Perpetual Unemployability."
And on, and on, and on...
So don't get all taken over by the vapors *now* just because I returned a *small* portion of your own attitude in kind by condescendingly calling you "hon"...
What a hypocrite you are... Have you no shame? Ah, hell, don't bother answering that -- you won't deal with it directly anyway, and the answer is already entirely obvious.
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