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.
"In a 1957 experiment that helped launch the modern study of language acquisition, the late Roger Brown showed that children know that if you say, "Can you see a sib?" you probably have in mind an action or a process. No other mammal seems to be equipped to use such clues for word learning.
Even more dramatically, no other species seems to be able to make much of word order. The difference between the sentence "Dog bites man" and the sentence "Man bites dog" is largely lost on our nonhuman cousins. There is a bit of evidence that Kanzi can pay attention to word order to some tiny extent, but certainly not in anything like as rich a fashion as a three-year-old human child."
"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."
Biology doesn't know in advance what the end product will be; there's no Stuffit Compressor to convert a human being into a genome. But the genome itself is very much akin to a compression scheme, a terrifically efficient description of how to build something of great complexity-perhaps more efficient than anything yet developed in the labs of computer scientists (never mind the complexities of the brain, there are trillions of cells in the rest of the body, and they are all supervised by the same 30,000-gene genome). And although there is no counterpart in nature to a program that compresses a picture into a compact description, there is a natural counterpart to the program that decompresses the compressed encoding, and that's the cell. Genome in, organism out. Through the logic of gene expression, cells are self-regulating factories that translate genomes into biological structure.
Dino-DNA injected into frog eggs would likely yield something different from dino-DNA in dinosaur eggs-because the micro-environment of the egg would inevitably influence which genetic cascades were expressed. (Fans of the environment shouldn't get too comfortable, either-implanting a frog's DNA into a dinosaur egg would be even less likely to yield a dinosaur.) Because the recipes that build the mind and brain are always sensitive to the environment, there is no guarantee that those recipes will converge on any particular outcome, and there will never be an easy answer to our questions about nature and nurture.
"In universities and pharmaceutical labs around the world, computer scientists and computational biologists are designing algorithms to sift through billions of gene sequences, looking for links between certain genetic markers and diseases. The goal is to help us sidestep the diseases we're most likely to contract and to provide each one of us with a cabinet of personalized medicines. Each one should include just the right dosage and the ideal mix of molecules for our bodies. Between these two branches of research, genetic and behavioral, we're being parsed, inside and out. Even the language of the two fields is similar. In a nod to geneticists, Dishman and his team are working to catalog what they call our "behavioral markers." The math is also about the same. Whether they're scrutinizing our strands of DNA or our nightly trips to the bathroom, statisticians are searching for norms, correlations, and anomalies. Dishman prefers his behavioral approach, in part because the market's less crowded. "There are a zillion people looking at biology," he says, "and too few looking at behavior." His gadgets also have an edge because they can provide basic alerts from day one. The technology indicating whether a person gets out of bed, for example, isn't much more complicated than the sensor that automatically opens a supermarket door. But that nugget of information is valuable. Once we start installing these sensors, and the electronics companies get their foot in the door, the experts can start refining the analysis from simple alerts to sophisticated predictions-perhaps preparing us for the onset of Parkinson's disease or Alzheimer's."