The Evolution of Imperfection: The Science of Why We Aren’t and Can’t Be Perfect

Hurst, an evolutionary genetics professor at the University of Bath, debuts with a stimulating examination of why genetic imperfections persist in humans despite tens of thousands of years of natural selection. Hurst argues that the prevalence of maladaptive genes in Homo sapiens can be traced to the fact that from one generation to the next, human genomes mutate more than most animals, but compared to, say, fruit flies, people live in smaller groups where the relative dearth of potential mates makes it more likely that deleterious mutations will get passed on. Some apparently harmful traits confer hidden benefits, Hurst writes, pointing out that the genetic contributors to sickle cell disease are thought to provide protection from malaria. Elsewhere, he explains that asexual reproduction would theoretically be more effective at perpetuating genomic lines than sex, but mammals likely developed the latter strategy as a means of culling harmful mutations. Hurst excels at teasing out the counterintuitive implications of natural selection, as when he examines how the evolutionary imperative for mothers to not waste resources on unviable embryos has led to the proliferation of embryo-killing genes that cause such prenatal conditions as Edwards and Patau syndromes, but his abstruse discussions of introns, codons, and other genetic mechanisms are tough to follow. Still, those who stick it out will be rewarded. (Apr.)