No one may be asked to treat Darwin as a belief system not open to revision, but sometimes there is a tendency to do so, as with other 19th century giants, such as Marx. "So as not to gainsay Darwin" sounded as if Steve might be in danger of falling into that.

It is evident that in some areas assumptions he made do need modifying, notably his ideas about 'the tree of life'. That is hardly surprising, we know a great deal more about some things than he possibly could - and there is still a great deal to learn.