In the sixth chapter of The Origin of pecies, Charles Darwin discusses a number of problem issues. These were issues which either bothered him or which he anticipated might bother his readers. One of these issues concerned how things of relatively little consequence, such as the tail of a giraffe, could be accounted for by his theory (Darwin, 1859, p. 162):

Organs of little apparent importance. … I have sometimes felt much difficulty in understanding the origin of simple parts… The tail of the giraffe looks like an artificially constructed fly-flapper…”

As we can see from the illustration, a giraffe’s tail is thin with a tuft of hair at its tip. It is relatively short and as such it does not appear to be even a very good fly-flapper. Yet, this tail is unique to giraffes and is similar for all giraffes. It is easy to understand Darwin’s concern about whether natural selection truly had the capacity to produce gradually something so unique yet so trivial.

Darwin’s concern was legitimate. Within a given population, natural selection has a limited capacity to work. For instance, it is intuitively obvious that in a population of 10,000 interbreeding individuals, it would be difficult for natural selection to deal simultaneously with 20,000 different issues, each trying to make its own impact for good or for bad. The ability of any one trait to make an impact would be diluted by competition from the others….

Continue Reading on