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 have never heard of him before. Seems he went "creationist" late in life but I have no information other than the creationists' websites which say what a great guy he was but give no credible links to his "accomplishments".
Would you rather have me lie to you and tell you that biological evolution includes origin of life?
Would you like me to lie to you and tell you the days in Gen 1 are 24 hr days?
Why would you want a minister that was a liar?
I love you so much that I tell you the truth instead of lying to you for money or telling you things I think you want to hear.
Aig is a creationist con game. There is no science there.
They lie to you.
What you perceive as rudeness is just a minister trying to get you away from the road to apostasy.
Even a dog knows the difference between a deliberate kick and being accidently stepped on.
Your "statistics" has been thoroughly refuted time and time again.
Your "statistics" has been thoroughly refuted time and time again
Yeah, right. So let me hear the refutation.
OK, so your vote is that all life came from a single cell?
Hmmm. Are you saying that the Creator was restricted in his design of the eye and that is why we have so many limitations?
I love you so much that I tell you the truth instead of lying to you for money or telling you things I think you want to hear.
And on that note of weirdness...I gotta go take 10mg of something...
I've been cheated. My cat can see better in darkness than I have.
The "wolphin" is the fertile offspring of a bottlenose dolphin and a false killer whale (which are different species from each other). This wolphin mated with a dolphin and produced a live baby. Kind of breaks the "absolute requirement" for differentiating species. :-)
From http://www.hotspots.hawaii.com/Wolphin.html :
This may not sound like big news, but when the "girl" is Sea Life Park's hybrid wholphin, Kekaimalu, it's pretty exciting! Her birth on May 15, 1985 was a big surprise for the Sea Life Park staff. Her mother, a bottlenose dolphin (Tursiops truncatus), and her father, a false killer whale (Pseudorca crassidens), met on the job in the Whaler's Cove show. Since they were two very different animals, it was not expected that they would produce an offspring, but they did, making Kekaimalu the world's only known living wholphin.
WAY-south Georgia.
no official wolf re-stocking has happened here.
otoh, we have dusky panthers, too, despite what "official" species range tables might say to the contrary. Not many of them, and I have never seen one, but they are here: I *have* seen their tracks, stropings, kills, traces, and scat.
there is a *reason* I go hunting whitetail with a bullpup AK47 with a 30-rnd magazine ;)
back to the Canis Family: IMO, dogs, coyotes, and wolves do not have sufficient genetic dissimilarity to be considered different species. That they don't often naturally interbreed doesn't matter - neither do Icelandic ponies with Shires, but both are still horses. Differences in temperament and morphology are likewise insufficient - there is more such variation among breeds of c.familiaris than there are between, say, a north american grey wolfe and a german sheherd.
IMO, "species" should denote a strict level of genetic incompatability when applied to sexually reproduced life forms.
but that's just me.
eventually, molecular biology will supplement/supplant Linnean taxonomy. until that time we all, laymen and scientists, shall have to just muddle along ;)
My cat can see better in darkness than I have.
All the better to poop in other peoples yards...
I can't make any claims about the human eye, but I can say that a smart four year old can design a better hinge joint than the human knee.
So.....where's the recipe?
Many current bacteria exchange genetic material. Research indicates there may have been a time when exchange was so pervasive there was no easy way to define individuals.. All this is hypothetical.
What isn't hypothetical is the evidence that all known life on earth shares a common DNA lineage.
remind me sometime to ask you (and RA, if he's game) for your take on the requisite physical implications corollary to Genesis 9:12-17, if one were to insist it is a literally factual record of history (as opposed to a story conveying moral truth - ie: a parable).
The human eye has TWO dead spots in low light conditions.
Can you do *nothing* but ad hominem attack? Rather than consider a view different from your preconceived one, you attack anyone with a perspective different from yours. This "discussion" is really getting too predictable....
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