On the Origin of Species that nature and human society were governed by natural laws. The "Origin of Species" as a book of wide general interest became associated with ideas of social reform. Its proponents made full use of a surge in the publication of review journals, and it was given more popular attention than almost any other scientific work, though it failed to match the continuing sales of "Vestiges". Darwin's book legitimised scientific discussion of evolutionary mechanisms, and the newly coined term "Darwinism" was used to cover the whole range of evolutionism, not just his own ideas. By the mid-1870s, evolutionism was triumphant. While
On the Origin of Species to be separate species produced fertile hybrid offspring freely, and in other cases what were considered to be mere varieties of the same species could only be crossed with difficulty. Darwin concluded: "Finally, then, the facts briefly given in this chapter do not seem to me opposed to, but even rather to support the view, that there is no fundamental distinction between species and varieties." In the sixth edition Darwin inserted a new chapter VII (renumbering the subsequent chapters) to respond to criticisms of earlier editions, including the objection that many features of organisms were not adaptive and could not