Darwin 200 - Damian Hirst on Damian Hirst's 'Origins' cover

A short article at the Guardian (Damien Hirst salutes Darwin's 'courage' in On the Origin of Species painting) initially passed me by.  It's by Hirst himself, and he says nice things about Darwin.  Apparently the painting is called ""Human skull in space", but while I quite like it, it's still not clear to me how it relates to the book.  Even after reading what Hirst has to say about it!