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.
Actually, every PhD (both men and women) I work with could care less about fame or "relevance" as you purport relevance. The relevance they are after is being able to add to the knowledge of the body of science. I am currently working on a joint paper with a colleague who completed his PhD in Astrodynamics. He is one of the nicest guys you will ever meet and couldn't care less about fame and/or fortune. All he wants is to make his tiny contribution in designing more efficient ways of flying spacecraft to planets in our solar system.
My Grandfather received his PhD in chemistry. But you will never find him on the web. Not even his name. Do you know what he did? He developed better and safer paints for homes. My dad received his PhD from the University of Wisconsin. He worked with the AEC back in the 50s and 60s. He too cannot be found on the web. However, he revolutionized uranium exploration. My uncle is rather famous (all over the web) but his PhD (same university as my dad) was in Geophysics. He became one of the leading researchers studying Antarctica. He wintered over there three times. He also has a mountain named after him down there. He too does not care for fame or fortune even though he is considered a leading expert in the world.
I work with PhDs every day and NOT ONE of them are after what you suggest.
For what it's worth, Chinese crossed a human and a rabbit. It was done in the lab and was not natural. And they evenutally aborted it. But it proves nothing.
For that matter they've crossed insects and plants. But again, it's unnatual and doesn't prove anything about evolution.
Basically then, what you are asserting is that the Bible, while true, doesn't necessarily tell us every single detail about the creation of the universe. Therefore, is it impossible that God, in the beginnning, arranged the laws of physics in such a way that the big bang would occur and inevitably lead to the formation of the earth and all life on it, including man? Couldn't the other "people" you mentioned in reference to the question about who Cain and Abel married be simply pre-human ancestors that were close enough to human to interbreed with the earliest humans? Couldn't being made in God's image refer more to the spiritual and mental capabilities of man, rather than physical ones? (ie. ability to think and reason, ability to make moral decisions, etc.) If you don't take everything literally in the Bible, and if you recognize that there can be things that aren't in the Bible, it opens up many possibilities, such as the possibility that science and religion really aren't contradictory.
Who, exactly, is trying to prove this?
*You* know -- those imaginary 'scientists' in her head. Just like the imaginary Halliburton executives who are pulling the strings on the Iraq war, at least according to the hallucinations of the nutbar liberals.
I didn't say that. I said "the beginning" and that's what scripture says. To me, the "beginning" clearly means the time when something starts or begins.
That would be Day One, NO?
Well, my Maine Coon is also a cat, but no way he's breeding with a female tiger. Though I'm sure he'd give it the old college try.
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.
Yes. Exactly.
This brings a certain surface appeal to your argument,
Translation: "Uh oh, that's undermining my point, I'd better try to hand-wave it away as just "a certain surface appeal", without actually refuting it..."
but the gap between type and species is a vast one.
Feel free to define it, then.
Your "leap" is still a huge one. Dogs are still dogs--goats are still goats.
Humans are still primates... Still apes too, for that matter.
I know that species are related--but your underlying assertion--"they arose from them"--is just not borne out as "proof" by any such list. Interesting, indicative, but hardly doctrine. I then pointed out what many people do to evo-shamans--that life dwindles rather than proliferates. Species decrease rather than increase. That there were more "then" and less "now" points to a speciation theory that lacks generative potency.
Each new day brings a story of a new "Eve" of our genetic ancestry, and the evos go into High Ritual Mode to worship their new goddess. A few months later, a new Eve and, with no spraining of cognitive dissonance, seems to be as welcome as the previous, abandoned, Eve was.
That the programming of life swaps around could be some very useful information for applied science--I'd just prefer that the scientists keep their religion to themselves.
How do you figure that? It was inaccurate, petulant, snotty, and devoid of any real substance other than arrogant "attitude". You go for that sort of thing?
If you built a robot which was designed to build a machine which produced a new product, who created the new product? The robot? The machine? No, I think it's pretty obvious that you created the new product. Similarly, if God created the laws of physics which made the big bang, evolution, etc. happen, then who created man? Evolution? The big bang? Nonsense, God created man in this scenario, just the same as if He had done so directly. If God created everything directly, then why does the Bible say it happened over a six day period? Why not just God spoke and everything was created immediately? The Bible implies that creation of everything was a process that required time to occur. It says that God created man on the sixth day. Therefore, man was created toward the end of the process. All of this is perfectly consistent with the idea that man is a product of evolution, the same as all the other species of life on earth.
"I get ya! And the animals that were being hunted developed defenses to protect them from the technological advancements of the hunter."
This a common misintrepratation of evolution. Organisms do not develop characteristics that protect them, those organisms that had the particular aspect which kept them alive will now be able to reproduce, an animal which does not have this certain protection will die off and not be able to breed. The following generations will most likely have this protection as well, those that do not will not live long enough to reproduce.
ROFL!!!!!! And 'bravo' on finding the *perfect* image to go with it.
Precisely what we'd expect if the theory of common descent were accurate. All life is a continuum. Alas, large chunks of are extinct, but as fossils are found, they fit right in. As predicted by the theory:
All present and fossilized animals found should conform to the standard evolutionary tree. And they do.
Fossilized intermediates should appear in the "correct" chronological order on the standard tree.
Nah. You are only talking 1 day. And God created light before he created the Sun.
In order to prove God didn't do what is recorded in Genesis, you have to know the extent of God's knowledge and abilities.
hmmm. Genesis is accurate because Noah's flood occurred. How do you arrive at the conclusion that the flood occurred?
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