Redrawn “tree of life” favors hot-origins theory
- From: Jeffrey Turner <jturner@xxxxxxxxxxxx>
- Date: Fri, 03 Mar 2006 19:40:55 -0500
http://www.world-science.net/othernews/060302_treefrm.htm
Redrawn ?tree of life? favors hot-origins theory
March 2, 2006
Courtesy European Molecular Biology Laboratory
and World Science staff
The most detailed ?tree of life? map yet devised boosts a theory
that the single-celled ancestor of all life forms dwelt
somewhere very hot, researchers say.
In 1870 the German scientist Ernst Haeckel mapped the
evolutionary relationships of plants and animals in the first
?tree of life.? Since then scientists have continuously redrawn
and expanded the tree, yet many parts have remained unclear.
Now researchers at the European Molecular Biology Laboratory in
Heidelberg, Germany, have developed a computer-aided technique
that they say resolves many of the open questions and produced
probably the most accurate tree yet.
The study is published in the March 3 issue of the research
journal Science.
?DNA sequences of complete genomes provide us with a direct
record of evolution,? said the laboratory?s Peer Bork.
He said that for a long time, overwhelming amounts of data?the
human genome alone contains enough information to fill 200
telephone books?thwarted efforts to make a detailed tree of
life.
Another problem has been the discovery that some microbes
exchange genes rampantly, blurring evolutionary lines. That,
some researchers say, could make it nearly impossible to map the
bottom of the tree.
But these problems ?can be tackled by combining different
computational methods in an automated process,? Bork said.
Researchers in his group identified 31 genes that exist in
various versions in 191 organisms, ranging from bacteria to
humans.
The scientists reconstructed the relationships among these genes
by analyzing their similarities, and trying to exclude cases
affected by the gene-swapping, called horizontal gene transfer.
Some theories hold that life arose in a hot environment such as
scorching springs at the ocean bottom, called hydrothermal
vents. Researchers said these theories may now get a boost.
The new computational procedure ?drastically reduced the ?noise?
in the data, making it possible to identify as yet unknown
details of early evolution,? said the laboratory?s Tobias
Doerks. ?For example, we now know that the first bacterium was
probably a type called gram-positive and likely lived at high
temperatures?suggesting that all life arose in hot
environments.?
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