This degeneration will continue until the
species has sunken into equilibrium, so to speak, with its
surroundings. Here natural selection works for degeneration. Sessile
animals have had a similar history. But these parasitic and sessile
forms had already been hopelessly distanced in the race for life.
Their presence cannot impede the leaders; indeed their survival is
necessary to directly or indirectly furnish food for the better
conformed. In the animal and plant world there is abundant room and
advantage at the top.
Once more, natural selection works as a rule for the survival of
individuals, only indirectly for that of organs composing, or of
species including, these individuals. It may work for the
development of a trait or structure which, while of no immediate
advantage to the individual, increases the probability of its
rearing a larger number of fitter offspring. Thus defence of the
young by birds may be a disadvantage to the parent, but this is more
than counterbalanced in the life of the species by the number of
young coming to maturity and inheriting the trait. Even here natural
selection favors the survival of the trait indirectly by sparing the
descendants of the individual possessing it. Natural selection may
always work on and through individuals without always working for
their sole and selfish advantage.
Pages:
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357