"We should be far more worried about "genetic enhancement"- efforts to artificially construct "improved humans." Here I side with Fukuyama: Although … - Gary F. Marcus

Instead, in our world, nature's contribution to development comes not by providing a finely detailed sketch of a finished product, but by providing a complex system of self-regulating recipes. Those recipes provide for many different things-from the construction of enzymes and structural proteins to the construction of motors, transporters, receptors, and regulatory proteins-and thus there is no single, easily characterizable genetic contribution to the mind. In the ongoing, everyday functioning of the brain, genes supervise the construction of neurotransmitters, the metabolism of glucose, and the maintenance of synapses. In early development, they help to lay down a rough draft, guiding the specialization and migration of cells as well as the initial pattern of wiring. In synaptic strengthening, genes are a vital participant in a mechanism by which experience can alter the wiring of the brain (thereby influencing the way that an organism interprets and responds to the environment). There are at least as many different genetic contributions to the mind and brain as there are genes; each contributes by regulating a different process.

To the extent that genomes can be thought of as compressed encodings of biological structures, they are spectacularly efficient. All the trillions of cells in the human body-not just the tens of billions in the brain-are guided in one way or another by the information contained in 30,000 or so genes. The best high-quality set of pictures of the body- the National Institutes of Health Visible Human Project, a series of high-resolution digital photos of slices taken from volunteer Joseph Paul Jernigan (deceased)-takes up about 60 gigabytes, enough (if left uncompressed) to fill about 100 CD-ROMs-and still not enough detail to capture individual cells. The genome, in contrast, contains only about 3 billion nucleotides, the equivalent (at two bits per nucleotide) of less than two-thirds of a gigabyte, or a single CD-ROM.

"To take one example, even a brief exposure to light in a newborn kitten, rat, or monkey can launch a complex cascade of gene expression. The light activates photoreceptors-which send signals-which trigger a pathway-which leads to the expression of neural growth factors and a set of genes known as "immediate early genes" or "early response genes"-each of which, in turn, triggers the expression of many more genes. One study of cichlid fish suggests that a change in social status (from submissive to dominant) is tied to changes in the expression levels of at least fifty-nine different genes-a phenomenon not entirely unrelated to the testosterone rush that Joe-six-pack gets when the home team wins."