Such questions used to be asked, and when they were asked, although
one might have a very strong feeling that it was not so, at the
same time one could not exactly say why. One could not then find
any scientific argument for objections to that point of view. But
with the further development of the question the whole subject
began gradually to wear a different appearance; and I am going to
give you a little bit of autobiography, because I think it may be
of some interest in this connection. I am going to mention two or
three of the successive stages which the whole question took in my
own mind as one thing came up after another, and how from time to
time it began to dawn upon me that I had up to that point been
looking at the problem from not exactly the right point of view.

When Darwin's "Descent of Man" was published in 1871, it was of
course a book characterized by all his immense learning, his
wonderful fairness of spirit and fertility of suggestion. Still,
one could not but feel that it did not solve the question of the
origin of man. There was one great contrast between that book and
his "Origin of Species." In the earlier treatise he undertook to
point out a _vera causa_ of the origin of species, and he did it.
In his "Descent of Man" he brought together a great many minor
generalizations which facilitated the understanding of man's
origin. But he did not come at all near to solving the central
problem, nor did he anywhere show clearly why natural selection
might not have gone on forever producing one set of beings after
another distinguishable chiefly by physical differences. But
Darwin's co-discoverer, Alfred Russel Wallace, at an early stage in
his researches, struck out a most brilliant and pregnant
suggestion. In that one respect Wallace went further than ever