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.
To recap as briefly as possible, there really should have been a New Fly by now. Not for this particular "scientist"--but because fruit flies have been the toys of geneticists for hundreds of years--tens of thousands of generations of flies in experiments--geographical isolation, as there have been scientists all over the world for decades playing with flies--thousands of attempts at selecting out for type and features.
Still, no new fly. It really should have happened, if it truly happens so easily in nature.
This article about hippos and whales would have been far better just adding to our knowledge of how species have astounding genetic ties. BTW--the interrelatedness of hippos/horses/whales has been well-known on other evidence for decades because of skeletal studies. These theories of how one species just POP out of another are laughable--and when "scientists" start making these wild extrapolations,it is to laugh.
I told you. I don't want to waste my time teaching you elementary biology. I will gladly leave you alone if you stop posting nonsense.
No, the theory of evolution stated that whales and hippos came from a single common ancestor. This recent finding lends more evidence to that idea.
Evolutionists have hundreds of millions of years to study the patterns of the evolution of species and apply this to the future. C'mon, it works both ways, what's my cousin the snail going to be when he is no longer a snail. He's going to have to be something!
Your keen analysis makes it more likely we are related to bananas.
Try reading for comprehension.
I suppose it was the prompting of the spirit which led you to post the above quotes?
On average a life form speciates about 3 or 4 times in a million years. I think you have awhile to wait before you will see a fly turn into some other "kind".
Yes, the Spirit of Truth.
You are bearing false witness again.
Sigh -- it's the SAME THING.
Consider this: You are descended from your cousin's grandfather, *and* your cousin is descended from *your* grandfather...
Think about it.
If you *still* have trouble with the concept, I have a nice two-by-four around here somewhere...
And what I said earlier is still valid, you guys must think people are stupid or something,
Well, that's certainly the way the evidence points, anyway...
but dont you dare call it science.
We call it science because it *is* science. If you disagree, feel free to explain why. Make sure you know what "science" actually is, first.
Sure, just tell me what environmental changes will take place in the future and what features that the modern snail lacks to deal with these changes. Your question is akin to me asking you what color hair your great, great, great, great grandchildren will have. You have no way of knowing now who subsequent generations of your descendents will marry and have children with. Therefore, at this time it is impossible for you to even pose a reasonable guess as to the answer to my question. That doesn't mean that the laws of genetics don't work. It just means that you have insufficient information to answer such a question. Similarly, there is insufficient information available to determine the future evolutionary course of any given modern organism. As I said earlier, absent any changes in the environment that modern organisms aren't able to currently deal with, there should be no evolution. Evolution makes no requirement that ALL species must undergo major changes over time. If an organism is well suited to its environment and that environment doesn't change, then that organism will remain relatively unchanged.
"Speciate", the verb of the day! Where's my dictionary! I'll use it in my next pick-up line.
Ouch, that'll leave a mark!
Again I pose my question.
If God has a hand in the affairs of men, (through inventions, rulers, sickness and politics, etc.), does it not make sense he could also have a hand in the affairs of animals.
Does God limit Himself to human affairs only? That would be kind of limiting, don't you agree.
I can't do any sort of double-blind study for three million years ago-- I can't prove you wrong, so you can't prove me wrong, either.
Stalemate.
In which case, I would advise these ersatz prophets of Eternity to tone down their sermonizing.
But, wouldn't you think, since we've been playing with fruit flies for about three hundred years...in Beijing, Detroit, Florence, Terra Fuego...and generations could well be in the hundreds of thousands...all those scientists playing Red Eye , Black Eye, Wingless, Albino with these flies ....
Wouldn't you think we'd at least get a New Fly, if the theory has anything to it at all? It'd sure bolster your religion and its dogma--which may be why so many scientists claim to have Given Life when they clearly have not.
No, since as anyone who's not completely ignorant on the subject already knows, evolution is a change in populations across generations, not a sudden functional alteration within a specific individual.
So are you just playing dumb -- or are you not playing?
The same question pertains to your amazingly uninformed rant about the fruit flies, too.
Well! I'll be a monkey's uncle! You sure said a mouthful there! But with all the hundreds of millions of years of evolutionary evidence and records of enviromental changes and predatory changes and all the history of all past changes if one wanted to could one SPECULATE on what that robin go after that worm will be 500,000 years from now? Is that enough time for him to speciate a couple of times? (my new word!)
Well, Darwin was right, but I wouldn't call him the greatest ever. It isn't like he invented the light bulb, ice cream, or general relativity.
Those are biggies, too! :P
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