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.
Theories are never proven, only partially confirmed or refuted. Evolution is an observed fact. The theory of evolution is the only candidate for a scientific explanation. The theory that the Entire Universe was creatied Last Thursday with the appearance of being ancient isnt't refutable but isn't science either; this theory can't be distinguished from the theory the Universe will be created Wednesday Next, either.
I don't care particularly whether evolutionary theory is correct or incorrect. If correct, it can be(and has been comercially) used to make useful predictions about the world. If incorrect, it will be replaced with something that works better.
No, it's a grouping of mathematical and biological views that describe apparantly fatal flaws in the construct that everything can be explained via random mutation and natural selection then posits that life designed by intelligence -- regardless as to how it was done -- is a more rational way of looking at reality.
I disagree. he referred to "the" inbreeding, not "YOUR" inbreeding
then again, I might have been mistaken
Not when you use the wrong formula.
For example: The number of ancestors required for me to have exist doubles every generation into the past, this must happen. 2 parents, one generation back, 25 years. Eight great-grandparents, 3 generations back 75 years.
20 generations back I must have had 1,048,576 grandparents, this is all in one generation of time,500 years ago.
30 generations back, 1,073,741,824 grandparents, of course evenly half men, half women. 750 years ago. 35 generations back it required 17,179,869,184 grandparents for me to exist as I am today.
You have not described exponential growth. You have only described the left-hand side of the parabola: f(x)=x^2
Populations tend to grow exponentially over time until they reach some bounds which limit their growth such as the amont of food or space available, at which time the growth flattens out.
The correct formula to describe ideal exponential growth is transcendential function using powers of e. The size of a population at any given time t with a starting population P and a growth rate of k can be expressed as P(t)=e^(k*t)
Using this equasion one can calclulate what the population will be at a certain time. Conversely, given the current population one can calculate what the population was in the past without reaching the false conclusion that there were many billions of people in the past for each person alive today.
This is a misuse of mathematics, either stemming from a lack of understanding of exponential growth, or a desire to disprove evolution, or both.
The Bible doesn't spell it out. Have you read it?
Too many people think too little.
Conservative leader Stephen Harper : you're outed?
sounds like balance... sounds like...
"the amount of ongoing thinking in the universe is a constant"?
;)
What do you interpret them to be made of?
Two things are infinite: the universe and human stupidity; and I'm not sure about the universe. -- A. Einstein
Excuse me, but...JEWISH FAIRY TALES???
(Rom 1:18 KJV) For the wrath of God is revealed from heaven against all ungodliness and unrighteousness of men, who hold the truth in unrighteousness;
(Rom 1:19 KJV) Because that which may be known of God is manifest in them; for God hath showed it unto them.
(Rom 1:20 KJV) For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead; so that they are without excuse:
(Rom 1:21 KJV) Because that, when they knew God, they glorified him not as God, neither were thankful; but became vain in their imaginations, and their foolish heart was darkened.
(Rom 1:22 KJV) Professing themselves to be wise, they became fools,
(Rom 1:23 KJV) And changed the glory of the uncorruptible God into an image made like to corruptible man, and to birds, and fourfooted beasts, and creeping things.
(Rom 1:24 KJV) Wherefore God also gave them up to uncleanness through the lusts of their own hearts, to dishonour their own bodies between themselves:
(Rom 1:25 KJV) Who changed the truth of God into a lie, and worshipped and served the creature more than the Creator, who is blessed for ever. Amen.
(Rom 1:26 KJV) For this cause God gave them up unto vile affections: for even their women did change the natural use into that which is against nature:
(Rom 1:27 KJV) And likewise also the men, leaving the natural use of the woman, burned in their lust one toward another; men with men working that which is unseemly, and receiving in themselves that recompense of their error which was meet.
(Rom 1:28 KJV) And even as they did not like to retain God in their knowledge, God gave them over to a reprobate mind, to do those things which are not convenient;
(Rom 1:29 KJV) Being filled with all unrighteousness, fornication, wickedness, covetousness, maliciousness; full of envy, murder, debate, deceit, malignity; whisperers,
(Rom 1:30 KJV) Backbiters, haters of God, despiteful, proud, boasters, inventors of evil things, disobedient to parents,
(Rom 1:31 KJV) Without understanding, covenantbreakers, without natural affection, implacable, unmerciful:
(Rom 1:32 KJV) Who knowing the judgment of God, that they which commit such things are worthy of death, not only do the same, but have pleasure in them that do them.
"the difference between genius and idiocy is that genius has its limits." - unknown wit
so, you gonna concede on the matter of the DiscoveryChannel "Eve" that you brought up, or are you gonna attempt rebuttal?
by the way, here is the full grotesque overstatement from DiscoveryChannel's official website:
"Eve Explained: Find out the science behind the theory that all humans alive today can claim as a common ancestor a woman who lived in Africa some 150,000 years ago."
not 20,000, but 150,000 years.
so, not merely "substantially older" than 6,000 years, but VASTLY so.
the rest of what I posted last night stands.
what the hell?
http://www.newscientist.com/article.ns?id=dn2716
patrilineal mitochondrial inheritance?
Excuse me, but the single mother gene came out long before Discovery channel aired any program. I heard this in the 80's.
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