http://www.scienceagogo.com/news/20060023224009data_trunc_sys.shtml24 January 2006
More Evidence Of Our Close Relationship With Chimps
The theory that humans and chimpanzees may be more closely related to each other than chimps are to the other two species of great apes - gorillas and orangutans - has just become even more compelling. Scientists at the Georgia Institute of Technology have found genetic evidence that supports the controversial hypothesis, suggesting that there is very little difference in certain regions of the human and chimp genomes.
Findings appearing in the Proceedings of the National Academy of Sciences seem to show that there is an ape-human evolutionary hierarchy, with chimps following closely on the heels of humans. Georgia Institute of Technology biologist Soojin Yi reports that the rate of human and chimp molecular evolution - changes that occur over time at the genetic level - is much slower than that of gorillas and orangutans, with the evolution of humans being the slowest of all. "For the first time, we've shown that the difference in the rate of molecular evolution between humans and chimpanzees is very small, but significant, suggesting that the evolution of human-specific life history traits is very recent," said Yi.
In a large-scale genetic analysis of approximately 63 million base pairs of DNA, Yi's team studied the rate at which the base pairs that define the differences between species were incorrectly paired due to errors in the genetic encoding process, an occurrence known as substitution. This slow down in the molecular clock correlates with a longer generation time because substitutions need to be passed to the next generation in order to have any lasting effect on the species.
Yi said that even though the 63 million base pairs they studied is a large sample, it's still a small part of the genome. "If we look at the whole genome, maybe it's a different story, but there is evidence in the fossil record that this change in generation time occurred very recently, so the genetic evidence and the fossil data seem to fit together quite well so far."
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