Newly detailed “tree of life” would boost hot-origins theory
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 lived 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 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 scalding 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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