Ape and Essence
Matt Ridley’s book is, as he puts it, “a whistle-stop tour of some of the more interesting sites in the genome and what they tell us about ourselves.” A British science journalist, Ridley is a lucid, engaging and enthusiastic guide to the double-helical DNA that comprises our inheritable human essence. He is the author of two previous books--”The Origins of Virtue” and “The Red Queen”--that deal with evolution, particularly the evolution of human nature and cooperation. “Genome” also attends to the history of our species as some scientists have found it revealed in our genes--the autobiographical reference of Ridley’s subtitle, its meaning enriched by commentaries extracted from comparison with the genes of other species.
In the main, however, Ridley leads us on a journey through the biology of human characteristics, focusing on data that bear--or at least are claimed to bear--on the genetics of physical, behavioral and mental traits. The data have come from a number of fields, including neuroscience, brain studies and research into the dynamics of the cell, but each has been increasingly informed by the dizzying acceleration in the acquisition and computer analysis of genetic information, not only about our own species but also about, notably, fruit flies, worms and mice.
Ridley, whose enthusiasm for genetics at times gets the better of him, asserts that “in just a few short years we will have moved from knowing almost nothing about our genes to knowing everything.” The fact of the matter is that, though scientists will shortly identify the sequence of chemicals that compose our genome and encode our humanness, it will be a long time before the functions of all our genes--we have perhaps 100,000--are understood. Nevertheless, we are learning much about ourselves from research on the genes of other species because a number of their genes are similar to ours in composition and function. The cracking of the genetic code sealed with chemical certainty our Darwinian affinity with the great apes. It also confirmed post-Darwin expectations that, as Ridley puts it, “all life is one; seaweed is your distant cousin and anthrax one of your advanced relatives.”
“Genome’s” 23 chapters nominally deal, one each, with our 22 non-sex chromosomes and with the sex chromosomes (X and Y). Pretty much ignoring the chromosomes in practice, Ridley takes one of the genes on each as a starting point to explore a trait to which it is putatively relevant. The real subjects of his chapters are characteristics such as intelligence, learning, instinct, self-interest, self-assembly (i.e., organismic development), disease, cures, personality, sex and memory.
Research in many of these areas has yielded fascinating results--for example, the discovery of “homeoboxes,” clusters of genes, many of them similar across species, that control the development of the fertilized egg into a multicellular, fully formed organism. “At the level of embryology we are glorified flies,” Ridley writes. At other levels, too: Studies with fruit flies have revealed genes that figure in memory and aging. Cancer has been exposed through studies of viruses, chicken cells and mice as a disease of genes gone wrong or made to go wrong by insults such as tobacco tar. One class of genes has been found--with implications for chemotherapeutics--to encourage misbehaving cells to commit suicide. DNA testing of seemingly monogamous birds has revealed that the female conceives children with males that are not her mate, a finding echoed in genetic testing for paternity among human beings.
Although such results are for the most part rock-solid--work in the genetics of development has won a Nobel Prize--some of the claims that Ridley reports in the genetics of behavior and psychology are questionable, to say the least. They include, for example, the detection of a linkage between male homosexuality and a stretch of DNA on the X chromosome; the correlation of super-brightness in a group of children with a sliver of DNA on chromosome 6; and the report that people with two long copies of a certain gene are distinctly more “novelty seeking” than people with two short copies of the gene. Ridley contends that a gene somewhere on the X chromosome “enhances the development of social adjustment”--for example, the ability to understand other people’s feelings--and he writes summarily that “the brain is an organ with innate gender.”
Genes no doubt figure in behavior, and such genes have likely been selected for survival over evolutionary time. But just how they so figure is extremely difficult to specify, and attempts to explain why they have survived natural selection often amount to speculative storytelling. Ridley’s stories may be captivating, but they are often merely stories, founded on a generally uncritical enthusiasm for evolutionary psychology. Some practitioners in that field hold, for example, that women’s dislike of sexual harassment lies in an evolved propensity to resist sexual overtures that is rooted in a preference for selecting the time and object of mating. Yet it’s easy to think of many nonreproduction-related reasons why women find sexual harassment offensive.
Still, Ridley is not a simplistic biological determinist on either the physical or the behavioral front. If he holds that genes play a role in intelligence, he insists that “heritability does not mean immutability,” pointing out that mental acuity can be improved by education and experience. He denounces the media’s elevating the identification of a genetic basis for language impairment into the discovery of “a grammar gene.” He emphasizes the interplay between the brain and the body, noting the commonplace that psychological and emotional stress can produce physical illness. “Far from behavior being at the mercy of our biology, our biology is often at the mercy of our behavior,” he observes.
Though some genes--for example, the one for Huntington’s disease--act implacably to kill or render us ill, the way others affect us depends strongly on their maze of interactions with the environments that we encounter and/or create for ourselves. “The more we delve into the genome,” Ridley writes, “the less fatalistic it will seem. Grey indeterminacy, variable causality and vague predisposition are the hallmarks of the system.”
Yet Ridley often gives the edge to genetic determinism and argues that, in the end, we can find comfort in thinking that we are shaped more by our genes than by our environment. Though environmental influences can express the tyranny of others, our genes are at least our own. We each have a human nature, Ridley declares, “flexibly preordained in our chromosomes and idiosyncratic to each of us. Everyone has a unique and different, endogenous nature. A self.” Small comfort, that, for those who prefer a plastic self--one that we can to some degree shape--to a genetically determined one.
