Evidence for Darwin’s Claim that Small Changes Can Accumulate Into Bigger Changes

By reconstructing ancient genes from long-extinct animals, scientists have for the first time demonstrated the step-by-step progression of how evolution created a new piece of molecular machinery by reusing and modifying existing parts.
The researchers say the findings, published today in the journal Science, offer a counterargument to doubters of evolution who question how a progression of small changes could produce the intricate mechanisms found in living cells.
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The researchers found the modern equivalent of the stress hormone receptor in lampreys and hagfish, two surviving jawless primitive species. The team also found two modern equivalents of the receptor in skate, a fish related to sharks.
After looking at the genes that produced them, and comparing the genes’ similarities and differences among the genes, the scientists concluded that all descended from a single common gene 450 million years ago, before animals emerged from oceans onto land, before the evolution of bones.
The team recreated the ancestral receptor in the laboratory and found that it could bind to the kidney regulating hormone, aldosterone and the stress hormone, cortisol.
Thus, it turned out that the receptor for aldosterone existed before aldosterone. Aldosterone is found just in land animals, which appeared tens of millions of years later.

For the full story, see:
KENNETH CHANG. “Study, in a First, Explains Evolution’s Molecular Advance.” The New York Times (Fri., April 7, 2006): A19.

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