Remarkably for those who came across it in the early days, this classic of popular science writing is now 50 years old - and like many of us who reach a certain age it has become somewhat overweight: a reasonable sized paperback has morphed into a 500-page monster. Even so, we have to recognise the importance of the book, despite its message not being as clear as it once was. One major change is that Dawkins, with his God Delusion hat on, was once the hero of the provisional wing of the progressive movement, where now he has been pushed aside for daring to suggest that there are only two sexes. The other change, of course, is that the science has moved on and some of the genetics certainties of Dawkins' day have reached the scientific stage of 'it's more complicated than we thought.' In a couple of chapters that weren't in the original book and about 120 pages of discursive end notes and an epilogue, Dawkins attempt to clarify some scientific developments and to c...