Bioinformatics allows all kinds of information to be gleaned about the gradual evolution of genomes. For example, it is clear that many genes have arisen from the duplication of an earlier gene, followed by a subsequent divergent specialisation of each duplicate under the pressure of natural selection.
New Scientist describes an interesting experiment to turn back genomic time, and to re-create the original gene that gave rise to two descendants. Moreover, that new "old" gene was shown to work perfectly well, even in today's organisms.
What's impressive about this is not just the way such information can be teased out of the raw genomic data, but that it effectively allows scientists to wind evolution backwards. Note that this is possible because the dynamics of natural selection are reasonably well understood.
Without the idea of natural selection, there would be no explanation for the observed divergent gene pairs, and the experimental fact that their putative ancestor does, indeed function in their stead, as predicted - other than the trivial one of saying that it is so because it was made so. Occam's razor always was the best argument against Intelligent Design.
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