The Clergyman's Wife and the Parrot

The so-called central dogma of biology is that DNA sequence is a code that specifies amino acid sequences via a messenger RNA (mRNA) intermediate in a one-way feed-forward transfer of information. It’s curious that scientists, who proclaim that everything is always open to question, would name one of our views a dogma, though it is certainly a wellestablished bedrock of biology that our genome hides, like the Prince of Pompadoodle, “behind a castle wall, behind a moat, behind a guard, of twenty soldiers tall,” because “somewhere in the palace was a cur who’d seek his end!”1 Chromosomes are tucked safely inside the protective barrier of the nuclear membrane, where their genes are transcribed into messenger RNA copies. Those copies leave the inner sanctum to venture into the dangerous world of the cytoplasm, where they are translated into amino acid sequences, which form proteins. The mRNA can be buffeted, degraded, and otherwise abused by cytoplasmic curs, while the princely integrity of the DNA itself is protected as the unchanged progenitor of the Dynasty. Actually, the central dogma does not require that DNA be physically guarded in this way. Bacteria are doing just fine without a nucleus (they’ll dance on all our graves, in the end). Instead, the protection is by a logical rather than physical moat: DNA is used as a stable source code to manage the changing operational material of a cell’s life. This has been viewed as a universal characteristic of genomes and in that sense is a dogma, I suppose. But evolutionary theory could easily withstand the Reformation that would follow the discovery that the dogma is not just so. What is much more critical to the current theory of life is not that DNA is unchangeable, because mutations have to occur at least occasionally as the fuel of evolution, but rather that no such change is instructed by the individual’s experience in a way that specifically improves its future prospects. Evolution is not teleological: It has no long-term goals. The inviolate credo is that genetic change is random with respect to any specific needs that the environment might present, and such variation is screened by the experiences of future generations to proliferate if it is helpful (natural selection) or lucky (genetic drift). A feedback of experience that modifies the DNA sequence in a specifically adaptive way would be that ultimate evolutionary bete-noire, Lamarckian inheritance. Most life scientists and even social scientists, including anthropologists, explain Lamarckian inheritance with lampooned images of giraffes mightily stretching their necks to reach the high leaves in a way that changes their genes so that they produce neckier offspring. That’s an inaccurate textbook caricature of poor Lamarck, as you can easily see for yourself by actually reading his 1809 book Philosophie Zoologique, available in English—and don’t worry, you won’t be heretically contaminated.2 Though ridiculed as a mystic by many, including Darwin, who had a vested interest, Lamarck anticipated most important aspects of Darwin and Wallace’s theory of evolution, only he did it 50 years earlier. (Darwin knew of the work and later suggested similar mechanisms of inheritance.) Lamarck stressed that his views were purely materialistic, not animistic, but he did believe that what an organism does during its life is transmitted to its offspring (today we’d say “in its genes”). This quite sensible way to account for familial resemblance can be traced at least as far back as Hippocrates, 2,400 years ago. Because Lamarck’s species modified their nature according to their needs, his “tree” of life (Fig. 1), perhaps the first ever drawn, did not include extinction. If he had had the advantagewe have, of a better fossil record and the evidence of the dodo and passenger pigeon, he would have had to accept that some lineages simply can’t stay with the program. But his idea that evolution is the result of striving to do well in one’s circumstances seems obvious if you think of what we see in everyday life: We do strive to do what we can do, and we do it with future objectives in mind, including objectives for the success of our children. Tomodern biology, this is a genetic illusion based on what we see in our short lifetimes compared to what can happen slowly over evolutionary time. According to the central dogma our behavior, or at least that of nonhuman species, who can’t set up college tuition savings accounts, is based on whatwe are, not onwhatwewant to be. Perhaps because of its intuitive appeal, and despite the central dogma, many investigators have searched for plausible Lamarckian mechanisms that would, after all, give organisms a Ken Weiss is Evan Pugh Professor of Anthropology and Genetics at Penn State University. E-mail: kenweiss@psu.edu