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.
"I still think you're making this extrapolation that the more someone learns about evolution, the more atheistic that person becomes."
It is more likely that, "The more creationist nonsense one is forced to accept to be a Christian the less likely someone will want to be one."
You meant confuses.
Evolution is a fact and the theory of evolution explains that fact.
http://www.talkorigins.org/faqs/evolution-fact.html
"Implicit in their argument is the idea that religion, or anything else that can't be proven with evidence, is nonsense."
What I resent is the attempt to fool people into thinking that religion has any evidence against evolution. You have just admitted that religion (creationism) should be kept out of science classrooms.
That is all that is necessary. You are free to believe anything you want and even tell your kids that life does not change over time. Of course, I doubt if they will make many contributions to biological science if they believe that.
I often wonder why creationists want to create a fantasy land for their kids that makes them ill-adapted to survive in a technical world.
"The theory of evolution is an exceptional case which involves religious and philosophical questions distinct from those present in other areas of science."
This idea is all based on a nonsensical interpretation of the Bible.
Evolution is a fact and the ToE explains that fact.
http://www.talkorigins.org/faqs/evolution-fact.html
"Scientific study of evolution doesn't appear to be objective."
This is so laughable it boggles the mind. Are you trying to say that misinterpretation of the Bible is more "objective" than 150 years of study of the mechanisms of evolution?
The only reason you cannot accept evolution as fact is your lack of objectivity based on a religious bias.
I would agree that this is a problem. However, the fault lies with those on the creationist side of the issue. Evolution, as a scientific theory, has a very narrow and specific definition. Evolution is defined as variation over time of allele frequencies in populations of organisms. This has been observed both in the wild and in the lab. There is no question that evolution occurs; it is as certain as any other scientific idea. The theory of evolution is the idea that this observed evolution is capable of accounting for all of the different species that currently exist and those that have existed. It makes no reference to a lack of design, to randomness, to a lack of belief in God or to any other idea that creationists seek to ascribe to it. The main mechanism for this process of speciation via evolution is theorized to be natural selection of genetic variants. The genetic variations may come from random mutations, genetic drift, or other processes.
I have maintained repeatedly that questions of design or God are unscientific because they are unfalsifiable. Therefore, the idea that evolution actually shows that design or God are not possible is an unscientific one which has no place in a scientific theory such as evolution. Any intellectually honest scientist should tell you the same thing. I think a lot of the venom in these debates arises from a confusion of the science with the scientists. I will readily admit that there are evolutionary biologists who will maintain that evolution shows that there is no God or no design. There have also been members of the Christian clergy who in the past have maintained that it is morally correct to torture and kill people who refused to believe in Christianity. These clergymen derived this belief by going beyond what Christian doctrine actually says. Similarly, scientists and others who argue against God or design on the basis of evolution go beyond what evolution actually says.
Having said that, evolution is still currently the only scientific theory regarding the diversity of life. ID and creationism are not scientific. If opponents of evolution can come up with another theory that explains observed data better than evolution and makes some testable predictions that are different from those made by evolution scientists will give it serious consideration. If these predictions hold true, then a new theory will be born. Admittedly, that's a pretty tall order, but that's why evolution is considered to be such a strong theory.
Nor is DNA the only shared feature of all life on earth (at least all life that we know of). The genetic code is identical for all life. That is, proteins are synthesized using a sequence of three DNA bases as a code for a specific amino acid. Each possible codon, or three base sequence, specifies some amino acid. The amino acid specified by a given codon in a human is the exact same amino acid specified by that same codon in a bacterium. That holds true for all possible codons. Furthermore, the basic chemical reactions that form the basis for metabolism are identical in all life forms. Glycolosis is the basic series of chemical steps that allows conversion of sugars into ATP. It proceeds via the same steps and using the same enzymes in both humans and bacteria. The Krebs cycle, which is a further energy producing mechanism, is identical in all aerobic (oxygen breathing) organisms. This would include all organisms other than some bacteria. The mechanisms of protein synthesis are also the same in all eukaryotes. On a fundamental level, all life is more similar than different. This is all explained quite naturally by evolution. What possible reason was there for God or some other designer to design us in a way that is so similar to bacteria or aquatic invertebrates or any of a number of organisms which live in a different environment and have completely different requirements?
I think you misunderstand the argument of the evolutionists. Those of us who are intellectually honest would never maintain that science is the only way to truth and that unscientific=false. However, we do see the good that science has done in the world and we do resent the attempts of creationists to replace a perfectly valid and reasonable scientific theory with unscientific ideas. It would be akin to trying to force all Chrisitian churches to throw away their Bibles and replace them with science texts. If creationists(/ID'ers) would just quit trying to claim that their ideas are scientific, I think that the intellectually honest people who see evolution as the best explanation for the observed data would be content to just let them believe what they want to. This also includes trying to push their unscientific ideas in science education as well. Allow science classes to teach evolution and teach ID/creationism in some other class. Stop trying to claim scientific status for ID/creationsm. If these two things were to occur, I would have no more reason to even argue the issue.
That's a pretty BIG '-'!! You were only off by a factor of 10^50 without it. Just to throw a monkey wrench, (and really give KP a big headache), have you accounted for the fact that if you lift both masses at the same time and drop them that the mass of the earth is different than if you lift, say the 1kg mass and leave the 5kg mass on the earth. Admittedly, the mass difference of 5kg is miniscule, but I just felt like being a smart aleck today.
Again, I note that you are setting up a strawman. The theory of evolution does not seek to answer metaphysical questions like 'what is truth.' Scientists do not claim this. They do claim that the theory of evolution is an explanation of why we see so many fossils of creatures which are very similiar but not exact to animals we see around us, and why we see so many so many fossils of animals who bear little resemblance to those alive today.
That's the prevalent idea among evolutionist (not just a handful of atheist scientist) - and it's regularly pointed out by them as an indication that their theory is superior to creation. That is where they take a turn towards ultimate immorality.
No, again you have set up a conflict between science and religion where there is none. Scientists do not point out that the theory of evolution is superior to creation. Scientists point out that the theory of evolution is superior to the theory of creationism.
Like what? If everything evolved there should be an abundance of intermediary fossils. This is why I say that scientist have broken away from core scientific principals and methods in defense of evolution. Let's look at the fossil evidence:
You have accused scientists of reaching a foregone conclusion, but here you have done just the same. There are numerous examples of transitional forms in the fossil record, from whales with hip-bones to mammal-like reptiles. Claims that there exist no transitional forms are directly contradicted by fossil evidence. There are veritable mountains of fossils in in every museum in America. Type in 'fossils' into google and you get about three million hits.
One of my favorites is the shark. We found one that swam the oceans 350 million years ago. I think it's safe to say that Cladoselache and the modern day shark are essentially indistinguishable. That's disappointing because if their fins haven't started to shrink away by now, we'll never live to see a shark with legs. Please take note of the fact that Cladoselache apparently didn't have parents either. 349 million years ago - nothing...........350 million years ago - POOF a damned shark. Wow.
There are four things wrong with this paragraph, which illustrate how you are incorrect. The first point is that there do exist fossils of early jawless fish. It's true that they are rare, and that there are gaps in the fossil record. However, there are gaps all through the fossil record. It is wrong to assume that forensic evidence would be laid out like a catering table. Two, it's also wrong to claim that the earliest shark-like fish of whom we've found a few individual fossils didn't have parents. Of course, they did. There are fragemtary fossils from older epochs that show both jawless and primitive jawed fish. Among these creatures are the ancestors of the shark. I'm sure you're aware that a skeleton of cartilage does not preserve as well as a skeleton of bone. We're extremely fortunate to have any fossils of early fish with soft skeletons. Thirdly, I looked up Cladoselache and it is wrong to say that it would be "essentially indistinguishable" from a modern shark. It had its mouth at the front of its head while modern sharks have their mouth below their nose. Fourthly and lastly, it's absurd to suggest that we should see sharks with feet. The shark is a highly successful apex predator. It is well suited to its environment. This kind of statement demonstrates a lack of understanding of natural selection and the role environmental stress plays on living organisms.
I found an illustration of Cladoselanche:
This is hardly "indistinguishable" from a modern shark.
Now, if you'll excuse me. You posts are becoming unpleasantly shrill. Good bye.
"Scientists point out that the theory of evolution is superior to the theory of creationism. "
Creationism is not a scientific theory. It is wishful thinking on the part of misinterpreters of the Bible.
I don't disagree. However, it is purported by some to be scriptually-based scientific alternative to the theory of evolution. Taken as such, most scientists would point out that the "theory of evolution" better matches the evidence than the "theory of creationism." Some creationists seem to interpret this as meaning the scientists want to trump religion.
Millions of what? False claims about the Bible?
I don't see how your lack of knowledge about science is my fault.
If your position is not based on a misinterpretation of the Bible, why do you object to evolution on religious grounds?
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.