SPLENDID ISOLATION:

The book's subject is one that has preoccupied the author for a long time but which tends to get only glancing references in other works on evolution: convergence, the phenomenon observed countless times in nature where specific body forms or other adaptations (everything from specialized noses to infrared light detection) are arrived at independently by the forces of environmental pressure and natural selection at unconnected times in unconnected species: fish and oceangoing mammals streamlining in many of the same ways, for instance, or echolocation being developed by many species, or the most spectacular example, flight itself, which has been independently achieved four different times in the history of life on Earth, although often through the same means:

In the case of birds, the path to the skies is clearer [than that of the Pterosaurs], but at first sight the convergences between at least the birds and the bats might seem to be superficial. Both flap their wings, and that is the end of the story? Not quite, when it comes to digestive physiology they show some intriguing similarities. The intense metabolic demands for flight are evidently also linked to a striking decrease in the size of the genome. This not only occurred independently in the birds and bats, but tellingly also in the extinct pterosaurs.

"The prospect of a more general theory of biology will depend on teasing out what unites form rather than divides it," Morris writes (noting, winningly, that "In the history of life, things not only change but they get decidedly more interesting"), and although The Runes of Evolution ranges into every detail of living things, one of the main unifying themes in these pages is the convergent evolution of minds, of higher cognition, which is always a dire gamble in evolutionary terms, since big brains take longer to grow than small brains and tend to gobble up enormous amounts of metabolic energy while being far less obviously useful than, say, bristling muscles or sharp fangs. Morris seems interested in all instances of convergence in the natural world, but the convergent development of intelligence seems to fascinate him particularly - even though (or because?) it leads mankind, in his view, into isolated territories. 

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