He who wishes to decide whether man is the modified descendant of some
pre-existing form, would probably first enquire whether man varies,
however slightly, in bodily structure and in mental faculties; and if
so, whether the variations are transmitted to his offspring in
accordance with the laws which prevail with the lower animals. Again,
are the variations the result, as far as our ignorance permits us to
judge, of the same general causes, and are they governed by the same
general laws, as in the case of other organisms; for instance, by
correlation, the inherited effects of use and disuse, etc.? Is man
subject to similar malconformations, the result of arrested
development, of reduplication of parts, etc., and does he display in
any of his anomalies reversion to some former and ancient type of
structure? It might also naturally be enquired whether man, like so
many other animals, has given rise to varieties and sub-races,
differing but slightly from each other, or to races differing so much
that they must be classed as doubtful species? How are such races
distributed over the world; and how, when crossed, do they react on
each other in the first and succeeding generations? And so with many
other points.
The enquirer would next come to the important point, whether man tends
to increase at so rapid a rate, as to lead to occasional severe
struggles for existence; and consequently to beneficial variations,
whether in body or mind, being preserved, and injurious ones
eliminated. Do the races or species of men, whichever term may be
applied, encroach on and replace one another, so that some finally
become extinct? We shall see that all these questions, as indeed is
obvious in respect to most of them, must be answered in the
affirmative, in the same manner as with the lower animals. But the
several considerations just referred to may be conveniently deferred
for a time: and we will first see how far the bodily structure of man
shews traces, more or less plain, of his descent from some lower form.
In succeeding chapters the mental powers of man, in comparison with
those of the lower animals, will be considered.
THE BODILY STRUCTURE OF MAN.
It is notorious that man is constructed on the same general type or
model as other mammals. All the bones in his skeleton can be compared
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