Archiver > GENEALOGY-DNA > 2006-05 > 1147906902

From: Jim T <>
Subject: New comparison of human and chimp DNA
Date: Wed, 17 May 2006 16:01:42 -0700 (PDT)
In-Reply-To: <>

This analysis looked at 800 times more DNA than previous ones.

Here are a few excerpts from the AP story about the research
which is to be published in a future issue of Nature:

"The researchers hypothesize that an ancestral ape species split
into two isolated populations about 10 million years ago, then
got back together after a few thousand millennia. At that time
the two groups, though somewhat genetically different, would
have mated to form a third, hybrid population. That population
could have interbred with one or both of its parent populations.
Then, at some point after 6.3 million years ago, two distinct
lines arose.

"For one thing, the new data suggest the human-chimp split was
much closer to the present than the 7 million year date that
fossils and previous studies indicate -- certainly no earlier
than 6.3 million years ago, and more likely in the neighborhood
of 5.4 million.

"The data also show that the human-chimp split probably took
millions of years. That's because in some parts of the DNA
sequence the genetic difference between humans and chimps is so
large that those genes must have been isolated from each other
nearly 10 million years ago. But in other places the human and
chimp lines are so close that they appear to have still been
swapping genetic material at least until 6.3 million years ago.

"One of those areas is the X-chromosome, which is intriguing.

"The genes that are a barrier to speciation tend to be on the
X-chromosome," said David Reich, the main author of the study.

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