"Human evolution," McKee writes, "has been the product of many forces that together made us neither inevitable nor probable." The same holds true for other species; with all due respect to Lamarck, McKee adds, the giraffe came to have its long neck by a roll of the genetic dice--but a roll that lent the giraffe a competitive advantage over its shorter-necked browsing cousins, and therefore one subsequently reinforced by natural selection. Illustrating his argument with the well-worn "butterfly effect"--wherein a butterfly flapping its wings in Europe can produce a typhoon half a world away--McKee examines the role of chance in the origin and decline of species, emphasising how unpredictable the dynamics of life can be even within the bounds of natural laws.

Within such disorderly circumstances, McKee observes, chance favours species that retain generalised features and behaviours; whereas, he writes, "the fossil record is littered with extinct primates that became too specialised," the ancestors of modern humans were broadly diversified, adapting to different niches and thriving in the bargain. Well written and written at an appropriately general level, McKee's book offers a useful survey of current evolutionary thought. --Gregory McNamee