possible for the several members of a species to have various
kinds of superiorities over one another. While one saves its life
by higher speed, another does the like by clearer vision, another
by keener scent, another by quicker hearing, another by greater
strength, another by unusual power of enduring cold or hunger,
another by special sagacity, another by special timidity, another
by special courage; and others by other bodily and mental
attributes. Now it is unquestionably true that, other things
equal, each of these attributes, giving its possessor an extra
chance of life, is likely to be transmitted to posterity. But
there seems no reason to suppose that it will be increased in
subsequent generations by natural selection. That it may be thus
increased, the individuals not possessing more than average
endowments of it must be more frequently killed off than
individuals highly endowed with it; and this can happen only when
the attribute is one of greater importance, for the time being,
than most of the other attributes. If those members of the
species which have but ordinary shares of it, nevertheless
survive by virtue of other superiorities which they severally
possess, then it is not easy to see how this particular attribute
can be developed by natural selection in subsequent generations.
The probability seems rather to be that, by gamogenesis, this
extra endowment will, on the average, be diminished in
posterity--just serving in the long run to compensate the
deficient endowments of other individuals whose special powers
lie in other directions, and so to keep up the normal structure
of the species. The working out of the process is here somewhat
difficult to follow; but it appears to me that as fast as the
number of bodily and mental faculties increases, and as fast as
the maintenance of life comes to depend less on the amount of any
one, and more on the combined action of all, so fast does the
production of specialties of character by natural selection alone
become difficult. Particularly does this seem to be so with a
species so multitudinous in its powers as mankind, and above all
does it seem to be so with such of the human powers as have but
minor shares in aiding the struggle for life--the aesthetic
faculties for example."--Spencer, "Principles of Biology,"
sec. 166.

Can thus natural selection,