The Descent of Man and Selection in Relation to Sex HTML version

General Summary And Conclusion
Main conclusion that man is descended from some lower form--Manner of development--
Genealogy of man--Intellectual and moral faculties--Sexual Selection--Concluding
A brief summary will be sufficient to recall to the reader's mind the more salient points in
this work. Many of the views which have been advanced are highly speculative, and
some no doubt will prove erroneous; but I have in every case given the reasons which
have led me to one view rather than to another. It seemed worth while to try how far the
principle of evolution would throw light on some of the more complex problems in the
natural history of man. False facts are highly injurious to the progress of science, for they
often endure long; but false views, if supported by some evidence, do little harm, for
every one takes a salutary pleasure in proving their falseness: and when this is done, one
path towards error is closed and the road to truth is often at the same time opened.
The main conclusion here arrived at, and now held by many naturalists who are well
competent to form a sound judgment, is that man is descended from some less highly
organised form. The grounds upon which this conclusion rests will never be shaken, for
the close similarity between man and the lower animals in embryonic development, as
well as in innumerable points of structure and constitution, both of high and of the most
trifling importance,--the rudiments which he retains, and the abnormal reversions to
which he is occasionally liable,--are facts which cannot be disputed. They have long been
known, but until recently they told us nothing with respect to the origin of man. Now
when viewed by the light of our knowledge of the whole organic world, their meaning is
unmistakable. The great principle of evolution stands up clear and firm, when these
groups or facts are considered in connection with others, such as the mutual affinities of
the members of the same group, their geographical distribution in past and present times,
and their geological succession. It is incredible that all these facts should speak falsely.
He who is not content to look, like a savage, at the phenomena of nature as disconnected,
cannot any longer believe that man is the work of a separate act of creation. He will be
forced to admit that the close resemblance of the embryo of man to that, for instance, of a
dog--the construction of his skull, limbs and whole frame on the same plan with that of
other mammals, independently of the uses to which the parts may be put--the occasional
re-appearance of various structures, for instance of several muscles, which man does not
normally possess, but which are common to the Quadrumana--and a crowd of analogous
facts--all point in the plainest manner to the conclusion that man is the co-descendant
with other mammals of a common progenitor.
We have seen that man incessantly presents individual differences in all parts of his body
and in his mental faculties. These differences or variations seem to be induced by the
same general causes, and to obey the same laws as with the lower animals. In both cases
similar laws of inheritance prevail. Man tends to increase at a greater rate than his means
of subsistence; consequently he is occasionally subjected to a severe struggle for
existence, and natural selection will have effected whatever lies within its scope. A
succession of strongly-marked variations of a similar nature is by no means requisite;
slight fluctuating differences in the individual suffice for the work of natural selection;
not that we have any reason to suppose that in the same species, all parts of the
organisation tend to vary to the same degree. We may feel assured that the inherited