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.
Nope, a Hoaglandite. Richard C. Hoagland.
Well-endowed placemarker
Okay, but this is a really cool article...despite Hill jokes and pics.
The swinging weight of a molten moon core would either have sent the moon flinging off into space or would have sent it crashing to earth.
Now this is where you begin to stumble. I found a site written for pre-teens (so it should be right up your alley) that covers this topic:
We know that the Moon has a very weak magnetic field. Oddly enough, this is fairly strong evidence that it does not have a molten core. Rotating planets or moons with molten cores will produce magnetic fields through "the dynamo effect." In a planet like the Earth, the molten core can flow freely in a process called convection. In addition, the Earth rotates, adding to the movement of the molten core. The flowing molten iron-nickel material can produce electrical current, which, in turn produces a magnetic field that surrounds the Earth. If the Moons core were molten , then it would have a field too, though it would be weaker. We only a detect a very weak field, much weaker than that expected from the dynamo effect.
Since small "moonquakes" have been measured, which probably originate in the core of the Moon, it could be partially molten. But for the reason described above, it can not be totally molten.
Much of the information in this reply can be found in Michael Seeds' _Foundations of Astronomy_, and probably several other astronomy and geology books.
Steve Bloom
for Ask a High-Energy Astronomer
I went ahead and highlighted the information for you so you don't have to struggle with all the big words.
Are you suggesting that Ichneumon's posts are polite? Now you are the one posting ignorant statements! Besides, my question is why you feel compelled to be so evangelistic. Why do you feel so compelled to convert someone you consider an idiot? Why do you feel the need to justify yourself to someone you have deemed an idiot?
I went ahead and helped you too.
I was ignorant but now enlightened. But I never realized it would lead to a "legalize drugs" essay ...
You need to define "kind."
You know, "kind of like a dog, kind of like a horse, kind of like a pig, kind of like a cow..."
Hey WT and Junior have decided to call me a bunch of names in the last few posts.
Better me than someone that can't handle it.
FReegards all.
I just hope that when the SHTF, we all stick together as conservatives.
No Creationist has been able to tell me what "kind" the animal in post 410 is.
I found part of this quote (the first clause, above) at the Quote Mine Project. It appears that, as you took this out of context, you were blatantly trying to make Dr. Wald appear to be saying something he really wasn't saying:
I am starting at the top of the center column on page 45.
One answer to the problem of how life originated is that it was created. This is an understandable confusion of nature with terminology. Men are used to making things; it is a ready thought that those things not made by men were made by a superhuman being. Most of the cultures we know contain mythical accounts of a supernatural creation of life. Our own tradition provides such an account in the opening chapters of Genesis. There we are told that beginning on the third day of the Creation, God brought forth living creatures- first plants, then fishes and birds, then land animals and finally man.
Spontaneous Generation
The more rational elements of society, however, tended to take a more naturalistic view of the matter. One had only to accept the evidence of one 's senses to know that life arises regularly from the nonliving: worms from mud, maggots from decaying meat, mice from refuse of various kinds. This is the view that came to be called spontaneous generation. Few scientists doubted it. Aristotle, Newton, William Harvey, Descartes, van Helmont all accepted spontaneous generation without serious inquiry. Indeed, even the theologians- witness the English priest John Turberville Needham- could subscribe to this view, for Genesis tells us, not that God created plants and most animals directly, but that he bade the earth and waters to bring them forth; since this directive was never rescinded, there is nothing heretical in believing that the process has continued.
But step by step, in a great controversy that spread over two centuries, this belief was whittled away until nothing remained of it. First the Italian Francisco Redi shoed in the 17th century that meat placed under a screen, so that flies cannot lay their eggs on it, never develops maggots. Then in the following century the Italian Abbe Lazzaro Spallanzani showed that a nutritive broth, sealed off from the air while boiling, never develops microorganisms, and hence never rots. Spallanzani could defend his broth; when he broke the seal of his flasks, allowing new air to rush in, the broth promptly began to rot. He could find no way, however, to show that the air inside the flask had not been vitiated. This problem was finally solved by Louis Pasteur in 1860, with a simple modification of Spallanzani's experiment. Pasteur too used a flask containing boiling broth, but instead of sealing off the neck he drew it out in a long, S-shaped curve with its end open to the air. While molecules of air could pass back and forth freely, the heavier particles of dust, bacteria, and molds in the atmosphere were trapped on the walls of the curved neck and only rarely reached the broth. In such a flask, the broth seldom was contaminated; usually it remained clear and sterile indefinitely.
This was only one of Pasteur's experiments. It is no easy matter to deal with so deeply ingrained and common-sense a belief as that in spontaneous generation. One can ask for nothing better in such a pass than a noisy and stubborn opponent, and this Pasteur had in the naturalist Felix Pouchet, whose arguments before the French Academy of Sciences drove Pasteur to more and more rigorous experiments.
We tell this story to beginning students in biology as though it represented a triumph of reason over mysticism. In fact it is very nearly the opposite. The reasonable view was to believe in spontaneous generation; the only alternative, to believe in a single, primary act of supernatural creation. There is no third position. For this reason many scientists a century ago chose to regard the belief in spontaneous generation as a "philosophical necessity". It is a symptom of the philosophical poverty of our time that this necessity is no longer appreciated. Most modern biologists, having reviewed with satisfaction the downfall of the spontaneous generation hypothesis, yet unwilling to accept the alternative belief in special creation, are left with nothing.
I think a scientist has no choice but to approach the origin of life through a hypothesis of spontaneous generation. What the controversy reviewed above showed to be untenable is only the belief that living organisms arise spontaneously under present conditions. We have now to face a somewhat different problem: how organisms may have arisen spontaneously under different conditions in some former period, granted that they do so no longer.
Wald spends quite some time dealing with the issue of the probability of life arising spontaneously. I again quote Dr. Wald (p47):
With every event one can associate a probability - the chance that it will occur. This is always a fraction, the proportion of times an event occurs in a large number of trials. Sometimes the probability is apparent even without trial. A coin has two faces; the probability of tossing a head is therefore 1/2. A die has six faces; the probability of throwing a deuce is 1/6. When one has no means of estimating the probability beforehand, it must be determined by counting the fraction of successes in a large number of trials.
Our everyday concept of what is impossible, possible, or certain derives from our experience; the number of trials that may be encompassed within the space of a human lifetime, or at most within recorded human history. In this colloquial, practical sense I concede the spontaneous generation of life to be "impossible". It is impossible as we judge events in the scale of human experience.
We shall see that this is not a very meaningful concession. For one thing, the time with which our problem is concerned is geological time, and the whole extent of human history is trivial in the balance. We shall have more to say of this later.
Wald then describes the difference between truly impossible and just very unlikely. His example is a table rising into the air. Any physicist would concede that it is possible, if all the molecules that make up the table act appropriately at the same time. ".but try telling one [a physicist] that you have seen it happen."
Finally, Wald cautions us to remember that our topic falls into a very special category. Spontaneous generation might well be unique in that it only had to happen once. This is the section to which I was referring in my previous post:
The important point is that since the origin of life belongs in the category of at-least-once phenomena, time is on its side. However improbable we regard this event, or any of the steps which it involves, given enough time it will almost certainly happen at lest once. And for life as we know it, with its capacity for growth and reproduction, once may be enough.
Time is in fact the hero of the plot. The time with which we have to deal is of the order of two [sic] billion years. What we regard as impossible on the basis of human experience is meaningless here. Given so much time, the "impossible" becomes possible, the possible probable, and the probable virtually certain. One has only to wait; time itself performs the miracles.
As I composed this, it came to me that here was a real authority on the spontaneous generation of life: Wald is a Nobel Laureate, his work on photopigments is classic. This is the perfect rebuttal to the Hoyle nonsense about tornadoes.
Finally, I would repeat that any errors herein are mine, except one. Dr. Wald estimated the age of the planet at two billion years. Since 1954 we have more than doubled that figure, based on new information. I can't help but think he is tickled pink at that kind of mistake.
- C. Thompson
It would help immensely if creationists would actually search for the actual source of their quotes instead of lifting them verbatim from some creationist website. The first "Christian" who edited these quotes to fit his agenda was as dishonest as the day is long. The folks who repeat the lies without double checking them are ignorant dupes at best or blatantly dishonest themselves at worst. Either option does not reflect well upon them.
Not me. I've never heard of Ted Holden.
BWAAA HAAA HAAA HAAAA!
If you have never heard of him, how did you know his name?
Probably, but not Camel Stroganoff.
Hubby has assured me that women can be called "well-endowed", too. So, yeah. :-)
I promise not to use Camel-milk.
The response was written to a third grader. Perhaps you are assuming too much.
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