 Biologist Theodosius Dobzhansky took issue with Kerkut's statements about evolution  where he comments “The basic conclusion of the author is, however, something else - since we cannot yet reconstruct in all of the details the phylogeny of the animal kingdom, therefore, evolution is not “proven”!This is a confusion of two distinct problems; we may be sure that life (or, for that matter, the Cosmos) had a history, but it does not follow that we know all the events of which these histories are composed, with their respective dates.The author has been wise not to suggest any alternatives to the theory of evolution...”.