Explore Evolution quotes Jonathan Wells, a senior fellow of the creationist Discovery Institute, in support the claim that "assembly instructions" are not solely in DNA. Inaccurately citing Wells as a "developmental biologist," the footnote quotes from Wells' creationist work Icons of Evolution, critiqued elsewhere on NCSE's website:
Developmental biologist Jonathan Wells has noted: "A skin cell is different from a muscle cell, which in turn is different from a nerve cell and so on. Yet with a few exceptions, all these cell types contain same genes as the fertilized egg. The presence of identical genes in cells that are radically different from each other is known as "genomic equivalence. According to Wells, this equivalence presents us with a paradox. "If genes control development, and the genes in every are the same, why are the cells so different?" Genes, says Wells, "are being turned on or off by factors outside themselves [C]ontrol rests with something beyond the genes ". Icons of Evolution (Washington, D.C., Regnery Press, 2000):191.Explore Evolution, p. 112
One could note that Zeno's paradox is not discussed in physics as a major problem in the study of motion, since the calculus of Newton and Leibniz solved the paradox. Likewise, this supposed paradox of "genomic equivalence" is not discussed as a major problem in developmental biology courses since it has been solved by the last 40 years of research in developmental biology.
If the genome is the same in all somatic cells within an organism (with the exception of lymphocytes; see Sidelights and Speculations), how do cells become different from one another? Based upon the embryological evidence for genomic equivalence (as well as bacterial models of regulation), a consensus emerged in the 1960's that cells differentiate through differential gene expression.Scott Gilbert (2003) Developmental Biology 7th ed., p. 92
This consensus view of development has been overwhelmingly supported by the discovery of genes such as Ultrabithorax which regulate other genes involved in developmental pathways. The claim by Jonathan Wells that genomic equivalence remains a paradox is another demonstration of how the anti-evolutionary arguments of the intelligent design movement embrace ignorance.