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.
You would think that one day a light would go off in their heads ...
Speaking of giraffes, the Bible neglected to mention the giraffe among the acceptable animals to eat.
Does not follow.
That's because scripture makes very specific claims.
So does the overwhelming evidence for evolution. And frankly, I'll take actual *creation* as being more of a final word on the matter than anyone's *interpretation* of any book.
I believe in the validity of science. I believe in the scientific method.
No you don't -- if you did, you'd follow the evidence where it leads, instead of frantically looking for excuses to ignore it.
But I don't believe that the scientists who have adopted evolution are correct.
...because the evidence clashes with what you want to continue to believe...
There is a portion of scientific thought (evolution) that is wrong.
Please provide the evidence for this assertion of yours.
It wouldn't be the first time and it wouldn't be the last time.
Wouldn't be the first time *you've* been wrong either, would it?
There are always just some ... dim bulbs and burnouts.
Why do you feel so compelled to prove that you are right? If you know for a fact that you are right, why must you so adamantly insist that you are right? Why can you not be content with knowing? Why must you be so evangelistic in your arguments? Why is it so important to you? Do you not realize how immature it is to belittle and antagonize people?
Thanks, nice collection.
And some locked to even more distant partners. Earth and Venus, for example.
I guess we just get tired of non-scientists bringing FALSE science and the Bible to these boards to disprove evolution and then when we discuss the Bible they tell us we are not qualified to discuss the Bible since we do not have the proper biblical education inorder to properly "interpret" the Bible.
signed,
Sub Sailor
Sort of like the possibility of evolution producing man is, hmmm, infinitesimal?
The original sets of animals that God made.
List them...
The representatives of which Noah carried on the Ark.
What evidence do you have that the ones Noah allegedly took onto the Ark are the same set(s) as the ones "original made"? What are "representatives" of those "kinds"? How did the marsupial "kinds" hike it over to Autralia after the waters receded? How do you explain the diversity within "kinds" that we see today, since generating that within just a few thousand years would require a HUGELY greater amount of "within-kind evolution" than creationists are willing to accept for standard evolutionary biology? Where did all the extra alleles come from? Which member(s) of Noah's family hosted the typhus, measles, smallpox, polio, gonorrhea, and syphilis "kinds" so that they wouldn't die out, and more interestingly, *WHY*? How many insect "kinds" were involved? What about them dinosaurs? There are 10,000 species of birds -- how many "kinds" was that? Since creationists claim that all the fossils in rock strata were laid down *during* the flood, how do you reconcile the "kinds on the ark" view with the practically limitless number of fosil species? How did all the plant "kinds" and fish "kinds" survive brackish water? How could more than a handful of "kinds" survive random influences that affect small populations? How were remote islands repopulated by "kinds"?
Now I know you'd like me to answer whether Noah carried both lions and tigers on the Ark or just representative cats. I don't know that.
Well okay then.
Reply: But the flood still happened which makes Genesis accurate and evolution false.
Perhaps you haven't been around enough to recognize that he was responding to DannyTN. He and others have been round and round with DannyTN and DannyTN does not respond to intelligent conversation. That was tried and it didn't work.
I've done both, they aren't that hard.
Sorry, but the Bible got the order *wrong* when compared to science...
Yes. One day science will have to give up on the preposterous notion that gravity causes synchronous orbit.
The moon pulls on the earth and the earth pulls on the moon but the twain never meet? Un-huh.
When the electromagnetic (push/pull) association of the planets is brought into the equation of celestial mechanics then synchronous orbit becomes not only mathematically possibly but expected.
...and another argument for ID becomes science!
Not just endowed, but well-endowed...
LMAO!
The Evolution of Improved Fitness by random mutation plus selection
I read this first example from your list. I believe you should remove it as evidence for evolution. In the article, at the start of section 2, the writer states:
Despite the logical fallacy in the creationists' dismissal of Dawkins's simulation, the seductive appeal of this argument led me to think that it could be most clearly countered if one could cite a biological example in which -- without the intervention of any intelligent designer -- successive rounds of mutation and selection could be unambiguously shown to lead to increased fitness within living organisms.He then goes on to explain current theory on how a portion of the human immune system works.
The implication is that if the body can splice genes to produce antibodies that increase an individual's fitness, then this is good evidence of a mechanism for evolution. But none of the antibody adaptations are inheritable. The gene rearrangements that produce the antibodies cannot be passed on genetically to offspring. Unless you are arguing for Lamarkian evolution, I propose that you remove this from your list.
Saturn overhead placemarker.
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