It can be very tempting to move from this observation of overlapping adaptation to the conclusion that evolution has followed a predictable, even deterministic course.
Others have laid stress on the concept of contingency. They argue that the tiniest event was capable of sending evolution down an entirely different path and that predictability is the last word we should apply to the chaotic story of natural history.
Until recently, advocacy of either position has largely rested on looking backwards from the range of flora and fauna we now have, ‘compiling lists’ of adaptations that support one case or the other, and engaging in thought experiments. As Jonathan Losos explains, scientists are now able to test their hypotheses directly. Evolution does not always ‘plod along at a snail’s pace.’ Adaptations can manifest themselves ‘quickly enough to document during the course of a five-year research grant’ and we are able to ‘study evolution as it occurs, right before our eyes.’
Losos explores the pioneers of this work and takes us on a fascinating tour of the research being conducted around the world: from those who measure the lengths of lizards’ legs to those who study microbes in the laboratory. This engagingly written and always even-handed book tells us a great deal about a world in which human and octopus eyes are ‘nearly indistinguishable’ but which has also been shaped by chance and unpredictable chains of causality. ‘Evolution repeats itself sometimes,’ Losos concludes, ‘but often it doesn’t.’ The powerful engine of natural selection and the ‘flukes of history’ have both played their part.