I am often asked what I think to be the best argument for intelligent design. From my vantage point as a biochemist, it's the genetic code. Recently published research adds to my conviction.
The genetic code resides at the heart of the cell’s chemistry. This code-universal to all organisms (at least to a first approximation)-consists of a set of rules. The cell's machinery uses these rules to convert the information stored in DNA into the information functionally expressed in proteins.
The Information Chain
Proteins-the "workhorse" molecules of life-take part in essentially every cellular and extracellular structure and activity. Proteins are chain-like molecules that fold into precise three-dimensional structures. And these structures determine each protein’s function. The molecular chains of proteins form when the cell’s machinery links together smaller molecules called amino acids. The specific sequence of amino acids dictates a protein's structure, and hence its function.
DNA houses the information the cell’s machinery uses to make proteins. DNA consists of two parallel molecular chains intertwined around one another in a helical fashion. The DNA strands are comprised of smaller molecules, called nucleotides, bound together like amino acids. The sequence of nucleotides signifies the amino acid sequences of proteins.
Experience teaches that intelligible messages-information-come from intelligent sources. A code requires someone to create it, and this common experience makes the genetic code a potent indicator of intelligent design. (See "What is a Code?" on page 8.)
So too does the genetic code's capacity to withstand errors caused by mutations. Even though mutations are potentially harmful, the rules that define the genetic code appear to be carefully constructed to minimize these errors. In fact, research indicates that the universal genetic code has a better error-minimization capacity than virtually any other conceivable set of rules that could have been used to construct the genetic code. Such radical optimization epitomizes intelligent design.
It doesn’t stop there. Recent work indicates that DNA harbors additional codes that overlay the genetic code. These codes consist of rules that independently direct the binding of histone proteins and transcription factors to DNA and dictate processes like messenger RNA folding and splicing. These code-driven critical activities regulate protein production. Again, a code requires a mind to create it. And multiple overlapping codes require a mind to structure them in such a way that they work in conjunction-instead of interfering-with one another. As if this evidence wasn't enough, another new study shows that the genetic code is also optimized to harbor the overlapping codes.
One study demonstrated that the co-expression patterns of genes for humans and chimpanzees differ considerably in the cerebral cortex but are largely similar in subcortical regions.2 Another study indicates that human and chimp genomes vary in microRNA (molecules that regulate gene expression) content.3 The way genes are regulated and expressed corresponds to the profound dissimilarities in human and chimpanzee brain structures and cognitive abilities (behavior), thereby explaining the crucial differences between humans and the great apes.
This amazing, life-critical code likely won't make any top ten lists in popular culture, but when it comes to evidence for intelligent design, the genetic code found throughout nature is simply "the best".