Posted on 12/03/2003 4:53:26 PM PST by Pharmboy
LONDON (Reuters) - Fossils discovered in Ethiopia's highlands are a missing piece in the puzzle of how African mammals evolved, a team of international scientists said on Wednesday.
Little is known about what happened to mammals between 24 million to 32 million years ago, when Africa and Arabia were still joined together in a single continent.
But the remains of ancestors of modern-day elephants and other animals, unearthed by the team of U.S. and Ethiopian scientists 27 million years on, provide some answers.
"We show that some of these very primitive forms continue to live through the missing years, and then during that period as well, some new forms evolved -- these would be the ancestors of modern elephants," said Dr John Kappelman, who headed the team.
The find included several types of proboscideans, distant relatives of elephants, and fossils from the arsinoithere, a rhinoceros-like creature that had two huge bony horns on its snout and was about 7 feet high at the shoulder.
"It continues to amaze me that we don't have more from this interval of time. We are talking about an enormous continent," said Kappelman, who is based at the University of Texas at Austin.
Scientists had thought arsinoithere had disappeared much earlier but the discovery showed it managed to survive through the missing years. The fossils from the new species found in Ethiopia are the largest, and at 27 million years old, the youngest discovered so far.
"If this animal was still alive today it would be the central attraction at the zoo," Tab Rasmussen, a paleontologist at Washington University in St Louis, Missouri who worked on the project, said in a statement.
Many of the major fossil finds in Ethiopia are from the Rift Valley. But Kappelman and colleagues in the United States and at Ethiopia's National Science Foundation (news - web sites) and Addis Ababa University concentrated on a different area in the northwestern part of the country.
Using high-resolution satellite images to scour a remote area where others had not looked before, his team found the remains in sedimentary rocks about 6,600 feet above sea level.
Oook, Oook! |
You are a shameless liar. Pathetic, as well as ignorant.
Find anything I have ever posted that justifies your moronic assertion.
Why not? This doesn't follow.
Here's a hint: We have no adequate test for determining that. The only studies we have are of purely matrilineal mitochondrial DNA.
Mitonchondrial DNA, in other words, says nothing about who your daddy was. There is no sexual recombination at all.
Why is that a problem? Some few hundreds of neanderthals here and there throughout Europe mate with those pesky new gracile, high-brow types swarming into the region. They aren't a big part of the mix, but they merge in.
Let's pick a male. He marries a Cro-magnon female. His kids get half his nuclear genes. How much of his mtDNA do they have? Not one of them has any.
Let's pick a female neandethal who marries a Cro-magnon male. Again, her kids each get half of their nuclear DNA from her. How much of their mtDNA do they have? All of them have all of it. "Now we're cooking!" you say.
But let's be real and say half of her brood is male. None of her granchildren from them will have neanderthal mtDNA. It's only her direct female line that will carry the mtDNA. She's only one woman in a village with maybe ten women in it, and the Cro-magnons think she's butt-ugly.
Chances are her mtDNA line will die out, even if her nuclear genes are spreading all over the place.
Not if the virus recently mutated.
You've been watching too many Tarzan movies. We don't know how many times the virus may have jumped to humans in some isolated population only to die out. Maybe zero. Maybe five.
After all this time, if survival of the fittest were true, they would not be dying.
It's far from clear that an African villager should have the same viral antibodies as a chimpanzee, but feel free to pursue that line.
Were the Spaniards then, superior to the Aztecs? Is that your belief?
I believe there was a high prevalance of smallpox antibodies in Cortez's crew and an absolutely zero prevalence of same in the Aztec population. Misunderstand that as you will. Points for creativity.
I'd love to if anyone knew. Since there are at least ten distinct varieties, and since it mutates readily, it's reasonable to assume the specific lethal human varieties are mutations of a form commonly found in chimps. Even if the original human infection was not a mutation, it has mutated since.
During most of the Cenozoic era, from the CretaceousTertiary boundary 65 million years ago [sic] until roughly 24 million years ago [sic], Afro-Arabia was [sic] an island continent drifting steadily [sic] northwards towards Eurasia. Fossil mammals documenting this period are scarce and belong almost exclusively to endemic forms restricted to Afro-Arabia, such as proboscideans, hyraxes and elephant-shrews. But by around 24 million years ago [sic], a permanent land bridge had formed between the two landmasses. A burst of faunal interchange followed: many Eurasian mammals, such as rhinos and ruminants, dispersed into Africa, and some Afro-Arabian mammals, such as elephants, migrated in the opposite direction. (Emphasis added in all quotations.)That forms the plot line, but there are problems. The Chilga specimens he describes seem to fit the story, but there are puzzles among the bones:
Among the proboscideans recorded are primitive [sic] forms such as Palaeomastodon and Phiomia (also known from older deposits in Egypt). But there are also representatives of modern families, for example taxa such as Gomphotherium, the earliest proboscidean on the branch leading to extant elephants. Another surprise is the oldest occurrence of deinotheres, peculiar proboscideans with downward-curved lower tusks, which were previously recorded only from rocks younger than 24 million years old [sic]. The new species of deinothere displays molars that are more bunodont in form (that is, made of several distinct cusplets arranged in transverse crests) than its descendant, whose molars display plain transverse crests. This discovery seems to rule out the possibility that deinotheres are derived from an ancestor bearing plain, transverse-crested molars, as was formerly supposed, and provides new evidence about proboscidean evolution [sic].Jaeger bemoans the scarcity of the fossil record for this period, but claims, Nonetheless, considerable information has been inferred from the evidence we do have. He talks about how systematists have grouped the African fauna into a superorder Afrotheria based on fossil and molecular evidence. Though African mammalian faunas are dominated by these endemic forms, a few other groups did get over to the big island somehow, including our alleged remote ancestors, the catarrhine primates, fathers of hominoids. These newcomers went through rapid evolution on the landmass, he claims.
Finally, the discoveries of Kappelman et al. highlight two other palaeobiological issues. First, on northern continents glaciation caused a significant cooling around 33 million years ago [sic], which resulted in numerous extinctions [sic] among mammalian communities. From these new data, however, it seems that large Afro-Arabian herbivores were not affected, either at that time or later, implying that the climatic changes were less severe on southern continents. Second, the fossil record of the Afro-Arabian continent is not only scanty but also largely concentrated on the northern edge. This has led to the proposal that other groups of mammals existed in Afro-Arabia during its period of isolation, but that they were restricted to more southern latitudes. However, the Chilga mammal community is rather like that found at Fayum in Egypt, which is some five million years older [sic], providing hints that there was little provinciality among Afro-Arabian mammals at that time. As yet, though, we have unveiled [sic] only a few of the secrets of mammal evolution on the Afro-Arabian continent. Many more surprising discoveries are to be expected.Got that?
Were going to give our readers an opportunity to go baloney detecting on this story before we have at it. Hint: separate data from storytelling, and look for the damaging admissions.Link
BS backatcha. I'm not talking about some YEC yesterday.
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