McMenamin takes up where Dolf Seilacher left off in theorizing that the Ediacara (precursors to the animals of the Cambrian explosion) were in fact a separate experiment in body plan, distinct from both plants and animals. He goes so far as to suggest that they may have independently developed nervous systems and sense organs. If McMenamin is right he is presenting evidence for the independent development of intelligence in more than one evolutionary lineage. Such a finding would have profound implications to our understanding of our place in the universe. Unfortunately, I didn't find his arguments very convincing. Seilacher has made a good case for the Ediacara having a unique and tough body plan unlike that of subsequent animals. Some Ediacara do show organs that may be heads--but to assert this is not to assert that they were heads, that they had nervous systems or sense organs. There may be plenty of other sensible explanations for Ediacaran body plans. We j! ust don't have evidence either way. As to the debate about whether the Ediacara were precursors of Cambrian animals or a separate line, there is no reason why they could not have been a separate evolutionary line; the fact that Ediacaran fossils are preserved in sediments that wouldn't preserve Cambrian-type organisms or soft-bodied creatures like worms suggests that a parallel development of animals with Ediacarans was possible, but simply isn't recorded. This is a very intriguing book, and obviously a very political one, designed to land like a bomb in the middle of the debate about Ediacara. As such I think readers should read it with some skepticism, bearing in mind that the Ediacara are almost the last virgin territory for evolutionary biologists to stake fundamental claims. If McMenamin is right it's groundbreaking stuff--but it's way too early to say.