IMPROBABLE DESTINIES

A fresh take on evolution and how “we can study [it] as it occurs, right before our eyes.”

Good books on evolution appear regularly. In this excellent book, Losos (Biology/Harvard Univ.; Lizards in an Evolutionary Tree: Ecology and Adaptive Radiation of Anoles, 2009, etc.), the curator of herpetology at Harvard’s Museum of Comparative Zoology, asks a big question that readers may not have considered: is evolution predictable? The author delivers an often startling, convincing, and entirely satisfying answer. In Hollywood science fiction, intelligent beings from distant planets look like us with a few tweaks. Science buffs sneer, but Losos maintains that this is reasonable. Provided the far-off planet’s environment resembles ours, life will evolve more or less in parallel. “There are limited ways to make a living in the natural world,” writes the author, “so natural selection drives the evolution of the same features time and again.” This is convergence, a process in which unrelated organisms develop similar traits as they evolve in similar environments. The iconic example: when a mammal and a reptile evolved to live in the ocean, the creatures (dolphin, ichthyosaur) looked alike and little different from a tuna. Even more startling, evolution itself has become an experimental science. A brilliant experimenter, Darwin never tested his greatest idea because he thought natural selection occurred at a glacial speed. In fact, when pressures are strong, species change visibly within generations. Losos devotes the second half of the book to juicy, hair-raising, if sometimes-tedious experiments in which scientists show evolution occurring before their eyes. Protected from grazing rabbits, plants run wild within years. Nearly 65,000 generations of bacteria, carefully observed over three decades, have undergone profound, permanent changes. Years of measuring lizard legs (the author’s specialty) or decades devoted to finch beaks or guppy color also turn up solid genetic transformation.

A cheerful, delightfully lucid primer on evolution and the predictive possibilities within the field.