SHELL, BEAK, TUSK

Heos (I, Fly, 2015, etc.) introduces convergent evolution by pairing different animals with similar physical traits.

The big, close-up animal photos here exert plenty of visual appeal (though the octopus opposite the parrot is viewed from an angle that hides its beak, the feature under discussion), and the author makes two worthy points. First, similar features can evolve in species that are geographically separate (at least today); and they can not only have similar uses, but sometimes, such as in the black-and-white patterns of penguins and orcas, serve very different agendas. She does not, however, either demonstrate that her selected traits evolved truly independently or explain why animals (and plants, come to that) that share similar foods and environments show such diversity of form. In fact her insistence that porcupines and echidnas, rabbits and bilbys, anteaters and aardvarks—all of which are mammals, after all—or even turtles and snails are “not related,” “not even distant cousins” seems as dogmatic as her initial claim that “only helpful” traits evolve. Neither is, in a broad sense, true.

An important aspect of evolutionary theory—though not presented with the author’s usual clarity of thought.