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.
This was addressed recently by a fellow named PeterBorger on the CvE forum.
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In the evolutionary community the shared retroviruses are commonly regarded as evidence of common descent. However, this may only be superficial.
First there is the claim that they do not serve any purpose. That should be scientifically proven. Maybe their function cannot be deduced from knocking them out, but that does not say anything about their function, since you can knock out genes with an open reading frame without any effect on the organism (genetic redundancies). Secondly, I would like to see the complete DNA sequences within the species and between the species before jumping to conclusions.
I checked one claim about the GLO pseudogene (the gene that catalyses the final step in vitamin c synthesis) that has been inactivated in the same spot in primates and is taken as proof for common ancestry. And, indeed a superficial look would immediately convince any evolutionist. However, if you have a careful look at the presented sequences you will discover that the replacement of nucleotides is not at random between the distinct species. Secondly, you will discover that it does not make a difference for the mutation rate of this gene whether it is functional or not, in contrast to what evolution theory would predict. Thirdly, it violates population genetics: why would the inactivated gene become fixed in the entire population, while the active gene conveys longivity. In addition, evolution never compensated for vitamin C uptake in the gut, and, finally, the gene is redundant anyway since the third step in vit c synthesis already yields vitamin C by spontaneous oxidation and is sufficient to avoid vit c deficiency. Also not unimportant, at least 2 primates are able to synthesize vitamin c in the liver, indicating the presence of an intact GLO gene (I once had a discussion about this gene with Dr D. Theobald (Talk Origin) so I know a bit about pseudogenes). However, at this level it is mostly speculation since we do not know a lot about it, yet.
In analogy to vestiges (appendix, tonsils) that shouldn't have a function according to evolution theory, it is far too early to say that this is proof for common descent. Show me the DNA sequences of these retroviruses in chimp and man, and I will respond in more detail.
Retrotransposons may have a function in epigenic regulation of gene expression (actually there is some proof for that. See: Dr. E. Max's website Talk Origin. Another one regulates the aghouti colour of fur in mice). It is thought that they may also play a role in eye colour (human), and some diseases like schizophrenia, and B.-W.-syndrome.
Evolutionists are free to claim these genes as evidence for common descent (as they did -- and still do -- for genetic redundancies, but which has actually contributed to the fall of natural selection as I will substantiate with scientific evidence in my forthcoming posting on genetic redundancy).
I foresee that ultimately there will be an unexpected (regulatory or stabilizing) function for these "vestiges".
Furthermore, read Spetner's book carefully on what he has to say on transposons. It makes sense. It will pay off to read opposite opinions. In summary, it is not an argument to take DNA sequences of which we do not know the function of as evidence for evolution. Our lack of knowledge described 98% of the DNA in the genome as "junk". This vision is increasingly proven to be wrong."
Note: link provided upon request.
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Nuts!
you mistake my objection.
the majority of high school students are incapable of summing a series of whole numbers or composing a compound sentence in English. They are thus incapable of understanding the distinction between faith and science, supposition vs. hypothesis vs. theory, fact and record/observation, etc...
the majority of teachers in the public education system are not competent to reliably teach a child how to tie his shoes. They are thus GROSSLY incapable of teaching so complex a discipline as evolutionary theory, let alone contrasting the science of evolutionary theory against the fraud that is ID.
fix the schools.
return Elementary school to its ordained purpose: firmly educating the young in the elemental skills of linguistics, logic, basic mathmatics, and the fundamentals of empiricism.
return High School to what it used to be: HIGH School - a place wherein properly prepared students can be led by competent teachers in exploration of much more complicated fields of study.
unless and until this is acheived, attempting to teach evolution in the public schools is at best pointless, and at worst highly counterproductive.
"However, if you have a careful look at the presented sequences you will discover that the replacement of nucleotides is not at random between the distinct species"
Exactly, that is why it must come from common descent.
This is exactly the type of Bravo Sierra that infuriates biologists and why most of them won't even address creationist nonsense.
a note of caution:
you must be careful not to use English words of Anglo-Saxon derivation to describe or denote bodily functions, excretions, or secretions. Such words are considered vulgar or obscene, and use of such on these fora can get your membership here revoked.
I find this a bit silly, but this site is not my property so I am constrained to abide by the rules of use established by those to whom this site belongs.
again: look up RING SPECIES
again: arctic seagull speciation
this is speciation from a common pool in action in realtime right now.
He is not going to study or listen to any science. Give it up.
"Note: link provided upon request."
OK, give us the link.
In the future, just give us the link and skip the nonsense.
True. I am just interested in what outside force is involved in the creation of order. Going back to the primordial ooze, parts of evolutionary theory indicate that randomly, a pot of gook organized itself to become living creatures. This high-level of organization is impossible to account for without and outside force in the partial system. What is the outside force? I know you do not know the answer, but this is the question I am trying to raise.
"Going back to the primordial ooze, parts of evolutionary theory indicate that randomly, a pot of gook organized itself to become living creatures"
WRONG! I suspect you know this is wrong.
this might be irrelevant, but: are you aware that much of what we call - and reliably use as - "order" is nothing more than an average of a great deal of disorder? generation of "order" and patterns from large numbers of chaotic events is commonplace.
Notice how many of the opponents of science claim not to be "creationists". Some claim not to be Christian.
But they all revert to the same old creationist arguments that have been debunked long ago and repeatedly.
I suspect some of these guys just do this to see how irritated they can get the scientists. I also suspect some of them are doing this to make Christians look stupid.
I will be interested to look into the links that have been provided and I will look for a satifactory answer to the questions I have raises. This is also something I would suggest that you do as well instead of calling names when someone challenges your ideas or stating "i am a biologist hear me roar".
In science there are facts that come from observation. These are called empirical data. In trying to explain observable phenomena, hypotheses are forumated. However, hypotheses are not just explanations that people dream up to fit the data. Vitally important to the process is that hypotheses are designed in such as way as to be testable and falsifiable. By this, I do not mean they can be faked. I mean that they are designed such that tested, and if the test fails then the hypothesis is shown to be false. Say that I hypothesize that all cats have five claws on each foot. This is a reasonable hypothesis to make. However, this hypothesis is falsified by finding a cat who has six claws on each foot. There is an uncommon genetic condition called polydactylism that is a trait in common housecats. One we have shown by empirical evidence that some cats have six toes on each foot, my hypothesis that all cats have five toes has been falsified. It is no longer valid.
Over time, if a body of evidence is compiled that supports a hypothesis, and predictions made from this hypothesis deliver useful results, it becomes a generally accepted theory. Evolution is one of these theories. Plate tectonics is another such theory, as is relativity. Evolution, plate tectonics, and relativity have had enormous impact on all our lives by advancing our understanding of biology, geology, and electronics. This is why it is wrong when people come in to these threads saying "Well, evolution is only a theory anyway." What they're saying is more like "evolution is only a hypothesis." Evolution is much more than hypothesis, much more than conjecture. Genes can now be seen to change over time. Not with the naked eye, perhaps, but with modern DNA sequencing technology we can now read the genetic code of organisms. This means we can compare the genes from one generation to the next, and quantifiably measure the changes that occurs over time in populations of organisms. All of these things support, and were predicted by evolutionary theory. The modern synthesis theory of evolution is the foundation upon which modern medicine rests. It's called the synthesis theory because it encompasses Darwin's theory of natural selection, Mendel's theory of inheritance, and the theories supporting our modern understanding of molecular biology and genetics including the discovery and description of the DNA chain by Watson and Crick. It's true that as new discoveries are made we need to revise the theory to better match the data we have, but overall the modern synthesis theory is supported by an enormous amount of empirical data. The challenge is not for me to "prove" evolution to you. The challenge is on you to provide data which totally invalidates evolutionary theory. Extraordinary claims require extraordinary evidence.
Is it impossible to raise questions on this board without getting flamed by idiots?
So Nada is the dada?
thank you.
the one who posits the sun as a source of patterned energy suppy to the partial system which could be a key organizing factor of large pools of random interactions?
-or-
the one who asks ""...the sun...", isn't that the fiery red ball in the center of the universe."
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