On the Origin of Species to be expanded with his research results and published if he died prematurely. In November 1844, the anonymously published popular science book "Vestiges of the Natural History of Creation", written by Scottish journalist Robert Chambers, widened public interest in the concept of transmutation of species. "Vestiges" used evidence from the fossil record and embryology to support the claim that living things had progressed from the simple to the more complex over time. But it proposed a linear progression rather than the branching common descent theory behind Darwin's work in progress, and it ignored adaptation. Darwin read it soon after publication,
On the Origin of Species to Races of Man", but did not add text on this topic. In "On the Origin of Species", Chapter VI: "Difficulties on Theory" Darwin mentions this in the context of "slight and unimportant variations": I might have adduced for this same purpose the differences between the races of man, which are so strongly marked; I may add that some little light can apparently be thrown on the origin of these differences, chiefly through sexual selection of a particular kind, but without here entering on copious details my reasoning would appear frivolous." When Darwin published "The Descent of Man, and Selection