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.
a quick scan does not indicate anything about exothermic chemical reactions converting mass into energy or endothermic chemical reactions converting energy into mass. I'll do a more thorough read later.
"1.5. The extreme size of this conversion figure was interesting in several respects. In the first place, it explained why the equiva-lence of mass and energy was never observed in ordinary chemical combustion. We now believe that the heat given off in such a combustion has mass associated with it, but this mass is so small that it cannot he detected bv the most sensitive balances avail-able. (It is of the order of a few billionths of a gram per mole.)"
The mousetrap was Behe's example. He wheeled that argument out again in a talk that I went to. He claimed that the mousetrap parts couldn't have been designed without being part of the mousetrap.
Another common misconception.
From the electrons. They are in a lower state after combustion. Of course, the mass loss is smaller than that lost in nuclear reactions; the energy is much lower.
This is an example of argument from incredulity, because irreducible complexity can evolve naturally.
And that's an example of an argument from credulity (or faith) i.e. It's irreducibily complex but evolution is true so it must have evolved or since evolution is true it's impossible for something to be irreducibly complex.
The bacterial flagellum is not even irreducible. Some bacterial flagella function without the L- and P-rings.
Now, this did not come up in my previous post addressing this subject but for a flagellum to function it needs the pump and motor, not the rings.
Yes, BUT he was arguing from design. The mousetrap is designed. You can't respond by saying "well this is how it could have evolved" without looking really stupid.
Talkorigins? That's like me linking to ICR.
"we now believe" as of 1940 but can't detect it with the technology of the day
got anything more recent?
I apologize. The phrase you used was "fellows that cooked up the Bible"
Thank you.
()Morton's Demon(/)
I was trying to supply something from the better minds of our times. Try this discussion of simple heating, not even a chemical reaction.
http://64.233.161.104/search?q=cache:6DWqpXmT8cEJ:fie.engrng.pitt.edu/eng12/Author/final/132.doc+combustion+mass+to+energy+conversion+e%3Dmc2&hl=en&ie=UTF-8
"Now we can reserve the relation E=mc2 and say that an increase of E in the amount of energy must be accompanied by an increase of E/c2 in the mass. It is very easy to supply energy to mass—for instance heat it by ten degrees. So why not measure the mass increase connected with this change? It is nearly impossible. Keep in mind that the speed of light is equal to three hundred million meters per second. Thus in calculating the mass increase, one would divide the energy by the speed of light squared. When such a big number is in the denominator, the quotient (or answer to division problem) tends to be very small. Thus an increase in mass does occur, but it is too small to be measured directly; even with the most sensitive balance."
Only by God's grace, the United States developed the atomic bomb before Nazi Germany or Imperial Japan.
The founding of our nation, and those who were involved in it were obviously divinely inspired.
The people in my life I am blessed with.
The wonders of nature.
The human feelings of hope, faith, love, charity, grief, despair is proof to me there is God. You may not understand this, but you may.
The many times in my irresponsible youth when I easily could have died, been maimed or contributed to it happening to others and it did not happen. Mere chance? I think not.
The wonder of seeing my small nieces and nephews during their most excellerated learning stage is wonder from God.
The miracle of breathing is a wonder from God.
The miracle of sight is a wonder from God.
When I'm able to work all day long at near 50 years old and realize the sun is setting yet again and God as blessed me with another day on His earth and I thank him, I know there is a God.
Great question, thank you.
What proof do you have that there is a God?
Another spell nazi.
No. You opened the subject of your spelling and posted that you should use a dictionary. I pointed out that there is an installed spell checker to aid you.
You posted that you enjoyed learning and I posted that apparently you had not learned from my post. I made NO comment about your spelling.
LOL. I'll take a pound of Mandlebrat. You know, Mandelbrot who created the procedures for getting Mandelbrot figures? It's generalized now.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.