Might we have this whole 'out-of-Africa' thing backward? That's Sundaland, folks, the same area where the new human species "The Hobbit" was found.
Posted on 04/02/2005 11:48:39 AM PST by blam
Infectious Evolution: Ancient virus hit apes, not our ancestors, in the genes
March 5
Bruce Bower
A vicious virus infected ancestral chimpanzees and gorillas in Africa between 4 million and 3 million years ago. Not only did it kill a great many of these primates, but it also infiltrated the surviving animals' genomes, altering the course of evolution. That's the picture emerging from a new analysis of modern-primate DNA.
Around 1.5 million years ago, this virus of the class called retroviruses also infected ancestors of modern baboons and macaques, two African monkeys, reports geneticist Evan E. Eichler of the University of Washington in Seattle and his colleagues. However, no molecular remnants of this ancient infection appear in the DNA of people, whose ancestors also inhabited Africa, or in the genes of apes, such as orangutans, from Asia.
Retroviral infection "was almost a cataclysmic event for ancestral chimps and gorillas," Eichler says. "It's a mystery to us why the ancestors of people and orangutans were excluded from it."
While analyzing data from an ongoing project determining the chimpanzee genome, Eichler's team noticed sequences that dramatically differed from corresponding regions of human DNA. The team identified the sequences as the remains of a retrovirus.
Using chemical probes, the researchers then found more than 100 copies of the retrovirus throughout the chimp genome. These retroviral sequences disturb the workings of at least six genes, including ones found in the brain and testes.
Gorillas, baboons, and macaques also possessed about 100 retroviral copies. The researchers used available estimates of how quickly the retrovirus mutates to calculate when the infections occurred.
Several scenarios could explain the selective infection of ancient chimps and gorillas. African apes might have evolved a susceptibility to the infection, for example, or ancestors of people and Asian apes might have developed a resistance.
The new results, which the researchers report in the April PLoS Biology, fit with a surprising conclusion floated in a 2002 analysis of chimp DNA. That study found a dearth of mutations in chimp genes known to be crucial for repelling infections. Pascal Gagneux of the University of California, San Diego and his colleagues then proposed that this genomic feature was a reflection of an HIV-like retroviral epidemic among ancestral chimps nearly 3 million years ago that left only a few to pass on rare resistance genes. Today's chimps are thus the offspring of unusually virus-resistant animals.
"Retroviruses are not just diabolical [killers]," says Gagneux. "Under the right conditions, such viruses contribute to the evolution of their hosts."
Eichler's group provides "compelling evidence" of separate, comparably ancient retroviral infections in ancestral chimps and gorillas, remarks Harvard University's Maryellen Ruvolo. Chimps probably came in contact with the virus when they hunted infected monkeys, Ruvolo suggests. It's not clear how the infection reached gorillas.
The new evidence that closely related primates can contract different retroviral infections is surprising, says Dixie Mager of the University of British Columbia in Vancouver. "Most people in the field would not have predicted this finding," she adds.
Scientists have estimated that 8 percent of human DNA consists of retroviral sequences that were deposited during infections of our African-ape ancestors between 35 million and 25 million years ago.
"It's a mystery to us why the ancestors of people and orangutans were excluded from it."
Maybe neither were in Africa when this was going on.
Also, has anyone ever noticed that Orangutans have the same shade hair as red-headed humans. Hmmmm...
Interesting. :-)
Cheetah, we hardly knew ye....
Might we have this whole 'out-of-Africa' thing backward? That's Sundaland, folks, the same area where the new human species "The Hobbit" was found.
Sundaland, an area twice the size of present day India went underwater at the end of the Ice Age. I wonder what kind of fossils lay down there? Hmmm?
Those Vikings sure got around, didn't they?
Could this information mean the the chimps and other primates
do NOT share the same DNA as most humans, and that this is genetic evidence that
they are not actually related?
I have noticed, that if the DNA sequences are similar, it
proves that there is an evolutionay connection, yet if some DNA sequences
are not shared it doesn't prove that there no connection.
Why this disparity in interpretation of this information?
Also, if some of our DNA is due to viral transfection, how
can anybody realistically say that analysis of DNA sequences
can prove any evolutionary connection (since all genomes could have
been selectively, and / or variably effected or "poisoned"?
It would greatly smear the geneitc lines of connections, leaving
it with a low probability to detect who was related to
who (genetic-wise)
Hence the name, Orang - utans
Bill Clinton laments that he is still married.
Yes. Our ancestors somehow avoided the plague, as did the orangutans. Chimps and baboons weren't so lucky. But I don't see anything here that contradicts the theory of common descent. Our hominid ancestors had already split off from the old stock by the time this event took place, so it wouldn't show up in our DNA. I don't know if this is a thread for the ping list.
"Maybe neither were in Africa when this was going on."
Heh... y'think?
"no molecular remnants of this ancient infection appear in the DNA of people, whose ancestors also inhabited Africa, or in the genes of apes, such as orangutans, from Asia"
Soon to be a GGG ping coming to a computer near you.
Primary Literature by Jonathan MarksThe Scars of Evolution"The most remarkable aspect of Todaro's discovery emerged when he examined Homo Sapiens for the 'baboon marker'. It was not there... Todaro drew one firm conclusion. 'The ancestors of man did not develop in a geographical area where they would have been in contact with the baboon. I would argue that the data we are presenting imply a non-African origin of man millions of years ago.'"
by Elaine Morgan
Please FREEPMAIL me if you want on, off, or alter the "Gods, Graves, Glyphs" PING list --
Archaeology/Anthropology/Ancient Cultures/Artifacts/Antiquities, etc.
The GGG Digest -- Gods, Graves, Glyphs (alpha order)
Please FREEPMAIL me if you want on, off, or alter the "Gods, Graves, Glyphs" PING list --
Archaeology/Anthropology/Ancient Cultures/Artifacts/Antiquities, etc.
The GGG Digest -- Gods, Graves, Glyphs (alpha order)
And apparently they weren't to selective either.
YEC INTREP
Tuesday, 9 January, 2001, 16:35 GMT
Fossil challenge to Africa theory
Bone fragments were examined for ancient DNA
Australian scientists say analysis of the oldest DNA ever taken from skeletal remains challenges the theory that all modern humans can trace their recent ancestry to Africa.
What our evidence shows is that the situation is much more complicated than any of these supporters of Out of Africa would have imagined
The study is based on the 60,000-year-old so-called Mungo Man skeleton, which was unearthed in New South Wales in 1974, and nine other anatomically modern Australian individuals who lived 8-15,000 years ago.
The Australian National University team looked at the DNA found in the mitochondria of these ancient people's cells. mtDNA, as it is known, is inherited only from females and also mutates - errors appear - at a steady rate, meaning it can be used as a "molecular clock" to investigate human history.
Mungo Man
Discovered at Lake Mungo in far west NSW in 1974 Had been covered in red ochre during a burial ritual Hands were interlocked and positioned over the penis Found in same area as cremated remains of female skeleton known by local Aborigines as Mungo Lady Recent lab studies of this type have suggested that our most recent common ancestor lived less than 200,000 years ago in Africa.
But the Australian researchers contend that the DNA sequences isolated from Mungo Man's bones show him to have a genetic lineage that is both older and distinct from this line.
Given the undoubted modern appearance of Mungo Man, they argue, major doubt must now be cast on the so-called "Out of Africa" hypothesis in which all living people are said to be descended from a group of modern humans who left their African homeland no earlier than about 120,000 years ago.
Alternative explanation
"What our evidence shows is that the situation is much more complicated than any of these supporters of Out of Africa would have imagined," lead researcher Dr Alan Thorne said.
Dating has put the age of the Mungo Man remains at between 56,000 and 68,000 years
"They were arguing that because the earliest forms of this particular genetic sequence in living people was found in Africa, that meant that all people must have come from Africa.
"Well, logically, that's not true anymore because we now have an older form of indisputably modern human that comes out of Australia."
Dr Thorne, whose team have published their research in the Proceedings of the National Academy of Sciences, is a proponent of the alternative, multi-regional explanation for the emergence of modern humans.
This suggests that modern humans arose simultaneously in Africa, Europe and Asia from one of our predecessors, Homo erectus, who left Africa more that 1.5 million years ago.
"Modern humans didn't just come from one area, they came from all areas," Dr Thorne said. "We assert that when people began to leave Africa about two million years ago, they were the ancestors of all modern people and we don't think modern humanity emerged from one place later on.
European studies
"We simply say that here we have a form much older than anything found in Africa and there's no evidence that it, or the skeletal anatomy of the fossil that it comes from, ever had anything to do with Africa. In fact, the skeleton looks very much like slightly earlier fossils that we know were in China."
Dr Alan Thorne supports the multi-regional explanation for the emergence of modern humans
But Out of Africa supporters are not about to let go of their beliefs because of the Australian research. Professor Chris Stringer, from the Natural History Museum in London, UK, said that, given experience with European fossils, there was some doubt over whether DNA analysis of such old samples was reliable. And he said the research community would want to see the work repeated in other labs before major conclusions were drawn from the Australian research.
But even assuming the DNA sequences were correct, Professor Stringer said it could just mean that there was much more genetic diversity in the past than was previously realised.
There is no evidence here that the ancestry of these Australian fossils goes back a million or two million years
Prof Chris Stringer, Natural History Museum "What it says is that some of that genetic diversity has been lost today," he told BBC News Online. "This sequence could have been in Australia and in Africa. In other words, it might have been in Africa 200,000 years ago, [it] came out with some of the African people and then got lost.
"There is no evidence here that the ancestry of these Australian fossils goes back a million or two million years, which is the multi-regional prediction."
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