The Ghosts of Evolution

April 9, 2001
In 1982, respected ecologists Dan Janzen and Paul Martin published a short, provocative paper in the journal Science, asserting that many fruits found in Central American forests "are adapted primarily for animals that have been extinct for thirteen thousand years." As those species went the way of the dodo, the fruits lost their initial means of dispersal, but continued to eke out a system of procreation, Janzen and Martin explained. Their insight led to the methodological realization that to fully understand the evolutionary forces shaping these fruits, scientists must first determine the behavior of the extinct animals. Science writer Barlow (From Gaia to Selfish Genes) extends this compelling idea into a narrative stretching from the Pleistocene era up through the inception, rejection and gradual, partial acceptance of this theory by the ecological science community. The large, pendulous seedpods of a honey locust, Barlow shows, evoke the ghosts of mammoths that used to disperse the seeds. Although there are some beautiful passages, too often the writing is precious and repetitive. Barlow details her own rather simplistic observations of certain plants—e.g., persimmon, osage orange and ginkgo—whose anachronistic existence is similar to the Central American fruits, but she does not contribute significantly to the underlying theory. Janzen and Martin explained their ideas in nine pages. Barlow, with 20 years of hindsight and 25 times as many pages, embellishes the story convincingly but doesn't add much new information. Photos not seen by PW.