While it might be nice to discuss the fact that
US military reserve capacity is broken, or to further
reflect on war crimes charges for US leaders, weazl thought it might be nice for a change of pace and think about science. Here's an interesting article from UK's Independent:
Early humans and chimps may have interbred to create hybrid man
By Steve Connor
Published May 18, 2006
The close relationship between man and chimp has just got cosier, according to a study which suggests that ancestors of the two species interbred at some point in the distant past to form fertile hybrids.
It is well established that chimpanzees are the closest living relative of humans but this is the first time that scientists have found evidence for hybridisation through interbreeding.
The astonishing conclusion comes from an exhaustive analysis of the genomes of humans, chimps, gorillas and monkeys published in the journal Nature. The researchers were particularly interested in the point at which the last common ancestor of man and chimp split into two separate species - the process of speciation that gave rise to the chimp and human lineages.
"The study gave unexpected results, about how we separated from our closest relatives, the chimpanzees," David Reich, of the Broad Institute of Harvard and the Massachusetts Institute of Technology, said. "We found that the population structure that existed around the time of human-chimpanzee speciation was unlike any modern ape population," he said. "Something very unusual happened at the time of speciation."
A comparison of the entire DNA of chimps and humans suggests that they split apart no more than 6.3 million years ago,far more recently than previously thought. The study found that an original split was probably followed by a phase of interbreeding and hybridisation, possibly with fertile female hybrids cross-breeding with male chimps, before the final split occurred.
Hybridisation is a common feature of how plants split into different species but scientists have not seen it as being so important in the speciation of animals.
The suggestion could explain why an early human-like fossil known as Toumai or Chad Man appears to date back to seven million years ago, before the split between chimps and man, Nick Patterson, a member of the research team, said. "The fact that the Toumai fossil has human-like features suggests human-chimp speciation may have occurred over a long period with episodes of hybridisation between the emerging species," he said.
The human genome carries the genetic information for making a human being but it also acts as a source of evolutionary history. Some parts of the genome are known to be older than others, meaning that they could date back to the common ancestor of chimps and man.
Dr Reich and his colleagues looked at the variation in evolutionary history across the genomes of humans and chimps. They found that the time from the beginning to the completion of divergence between the two species ranges over more than four million years, much longer than expected. In particular, the study found that the X chromosome - which occurs twice in women and once in men - is the youngest part of the genome and was still being modified just before the final split occurred.
"A hybridisation event between human and chimpanzee ancestors could help to explain both the wide range of divergence times seen across our genomes as well as their relatively similar X chromosomes," Dr Reich said. "That such evolutionary events have not been seen more often in animal species may simply be due to the fact that we have not been looking for them."
The close relationship between man and chimp has just got cosier, according to a study which suggests that ancestors of the two species interbred at some point in the distant past to form fertile hybrids.
It is well established that chimpanzees are the closest living relative of humans but this is the first time that scientists have found evidence for hybridisation through interbreeding.
The astonishing conclusion comes from an exhaustive analysis of the genomes of humans, chimps, gorillas and monkeys published in the journal Nature. The researchers were particularly interested in the point at which the last common ancestor of man and chimp split into two separate species - the process of speciation that gave rise to the chimp and human lineages.
"The study gave unexpected results, about how we separated from our closest relatives, the chimpanzees," David Reich, of the Broad Institute of Harvard and the Massachusetts Institute of Technology, said. "We found that the population structure that existed around the time of human-chimpanzee speciation was unlike any modern ape population," he said. "Something very unusual happened at the time of speciation."
A comparison of the entire DNA of chimps and humans suggests that they split apart no more than 6.3 million years ago,far more recently than previously thought. The study found that an original split was probably followed by a phase of interbreeding and hybridisation, possibly with fertile female hybrids cross-breeding with male chimps, before the final split occurred.
Hybridisation is a common feature of how plants split into different species but scientists have not seen it as being so important in the speciation of animals.
The suggestion could explain why an early human-like fossil known as Toumai or Chad Man appears to date back to seven million years ago, before the split between chimps and man, Nick Patterson, a member of the research team, said. "The fact that the Toumai fossil has human-like features suggests human-chimp speciation may have occurred over a long period with episodes of hybridisation between the emerging species," he said.
The human genome carries the genetic information for making a human being but it also acts as a source of evolutionary history. Some parts of the genome are known to be older than others, meaning that they could date back to the common ancestor of chimps and man.
Dr Reich and his colleagues looked at the variation in evolutionary history across the genomes of humans and chimps. They found that the time from the beginning to the completion of divergence between the two species ranges over more than four million years, much longer than expected. In particular, the study found that the X chromosome - which occurs twice in women and once in men - is the youngest part of the genome and was still being modified just before the final split occurred.
"A hybridisation event between human and chimpanzee ancestors could help to explain both the wide range of divergence times seen across our genomes as well as their relatively similar X chromosomes," Dr Reich said. "That such evolutionary events have not been seen more often in animal species may simply be due to the fact that we have not been looking for them." Original article posted here.
5 comments:
Anthropology has always been one of my favorite subjects. Three more hours and I would have had a minor in anthropology.
Sometimes I still wish I majored in Anthro.
Since DNA has been used, there has been major changes in how we look at human evolution. Mitochondrial DNA shows modern man may have been developed around 2 million years ago. It also shows that all humans outside of Africa developed from one group that left Africa.
(Mitochondrial Eve) It also shows that there has been more than one exodus from Africa, but only the last one was successful...somewhere between 60 and 80,000 years ago.
Interestingly, there may have been three different types of man living during the same time period..modern man, Neanderthal, and Homo Erectus.
I've seen some claims that Homo Erectus might be a direct ancestor to the "hobbits" that lived in Indonesia up to 12,000 years ago.
Neanderthals died out around 26,000 years ago in parts of Spain and Portugal.
We split off from gibbons and orangutans around 15 million years ago...Ramapithecus has been proposed as being that evolutionary tree. Since we are 98% genetically consistent with chimpanzees, splitting off 6.5 million years ago doesn't sound far-fetched.
My only question is that the definition of a species is that it cannot interbreed with members of other species. 6 1/2 million years ago, they might still be members of the same species.
I should have known better..
From Aljazeer
> Home > Middle East Review
Chavez proclaims end of U.S. Empire
5/16/2006 1:30:00 PM GMT
Chavez speaks at the Camden Centre London, during his arrival in Britain
Venezuela’s leader Hugo Chavez, who has just paid a visit to London, announced plans to ship his country’s oil to the needy, and declared that the “final days of the North American empire” are drawing near.
Come on weaz, I expect better than that.
Wow, AC, I wouldn't have thought you to have been an "out of Africa" man. Very nice. I'm impressed.
As far as Chavez goes, I agree with his main point: our glory days are behind us. Not controversial.
lmao...don't tell me you thought I was a Bible thumper.
As far as our glory days being over, I remember hearing the same thing back in the 1980s when Japan was becoming a world economic power. If things continue down the road we are following, then you may be right but American ingenuity has overcome many doubters before.
We are still near or at the leading edge of most technological advances. If we break our dependence on fossil fuels who knows what might happen.
This is what makes me angry when we let other countries take the lead in stem cell research or any BioTechnology.
No, didn't think you were a thumper, but thought you might have let your political biases squeeze into hard sciences. And the Out of Africa debate has been quite politicized, especially as compared to other scientific debates.
As far as Japan goes, our economic policies of "liberalization" did Japan in. China is not going to succumb to the US pressure, so a repeat of the 90's Japanese economic decline (coupled with the extraordinary birth and rise of the internet) is not likely to happen this time around.
And the mounting economic and political problems make such a resurgence that much more unlikely.
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