Darwin's Doubt: The Explosive Origin of Animal Life and the Case for Intelligent Design

by Stephen C. Meyer

When this occurs, one of the two genes may begin to vary—to experience mutations—without adversely affecting the function of the organism, while the other performs the original function. In the jargon of evolutionary biology, mutational changes in gene duplicates are “selectively neutral”—they initially provide no advantage or disadvantage to an organism or population. These gene-duplication events allow nature room to experiment safely. Unhelpful but harmless genetic novelties can be passed on to future generations, where additional mutations one day may render the evolving genetic material useful. Eventually, as mutational changes accumulate, a new gene sequence may arise in a new organism that can code for a novel protein fold and function. At that point, natural selection can favor the new gene and its protein product, preserving and passing it along to future generations—or so the story goes. This scenario—which many evolutionary biologists now refer to as the “classical model” of gene evolution—has the advantage of allowing portions of the genome to vary freely through many generations, giving mutations many opportunities to “search” the space of possible base sequences without being punished for drifting into valleys of lost or diminished function. But this scenario faces an overriding problem: the extreme rarity of sequences capable of forming stable folds and performing biological functions. Since natural selection does nothing to help generate new folded, functio...