ology, and fossil history of
the human species, in order to see that there is ample proof of the actual
occurrence of evolution, and then, as before, we may look about for the
causes which have produced this result by natural methods.

While it is necessary to treat the subject directly, namely, by examining
the actual evidences relating to the particular case in question, it is
worthwhile before doing so to point out that, as the whole includes a
part, human evolution has already been proved beyond question. This
conclusion must be accepted, unless reasons can be given for excluding
mankind from the rest of the living world as an absolutely unique type,
supreme and isolated because of some peculiar endowments not shared with
the rest of animate nature. If these reasons are lacking, and the unity of
organic nature be recognized, human evolution cannot be denied unless some
interpretation more reasonable and logical than evolution can be given for
the whole mass of facts exemplified and discussed in the foregoing
chapters. We may accordingly approach the main questions by asking if
there are any reasons for regarding the human species as a unique and
isolated type of organism.

At the outset, we must recognize that in so far as the human body is
material, its movements and mass relations are controlled by physical
principles, like all other masses of matter. It is well, indeed, that this
is so, for if gravitation and the laws of inertia were not consistent and
reliable principles holding true at all times and not intermittently, it
would be difficult to order our lives with confidence. In the next place,
the general principles of biology hold true for the structure and
physiology of the human species as they do for all other living things. A
human body is composed of eight systems of organs, whose functions are
identical with the eight vital tasks of every other animal. All these
organs are made up of cells as ultimate vital units, and the materials of
which human cells are composed belong to the class of substances called
protoplasm. Human protoplasm, like all other living materials, must
replenish itself, and respire and oxidize in obedience to biological laws
that have been found to be uniform everywhere. Thus the human organism is
no more unique in fundamental organic respects than it is apart from the
world of physical processes and laws.

How does the matter stand when the general structural plan of a human
being