I have to criticize the video below. It’s a beautiful piece of work, and the animal it shows is spectacularly well-adapted, but it does not demonstrate the fulfillment of a uniquely Darwinian prediction.
An orchid was found with a nectary that was only accessible by way of a long, narrow tube, and Darwin predicted the existence of an insect pollinator with an almost equivalently long tongue. However, an Owen or a Cuvier, scientists of that century who did not accept evolution, could have easily made the very same prediction, on the basis of created functionality: a god would not have made the flower that way unless he also, in his infallible foresight, also made a complementary pollinator. One could also make an argument based on an orchidized version of the anthropic principle: the flower is there, therefore it must have been produced by a parent flower that had been pollinated, therefore there must exist a long-tongued pollinator.
The special Darwinian character comes from the explanation of how such a phenomenon came to be; not by the fiat of some arbitrary creator, but by a set of processes that must still operate. It is to the advantage of the flower that the pollinator has to struggle a bit to reach the nectar reward, pressing itself against the flower and covering itself with pollen, while the pollinator would prefer to be able to reach in easily and without mess and fuss to get its dinner. This means that there is selection for flowers that have slightly longer nectary tubes than the insect tongues, while there is selection for insects that are able to reach all the pools of sweet nectar — but this is a race in which the insects will always be slightly behind.
What Darwin predicted was not a perfect match between nectary and proboscis, but that the insect proboscis would be slightly shorter than the nectary, and that’s what you find in his work On the Various Contrivances by which British and Foreign Orchids are Fertilised by Insects, and the Good Effects of Intercrossing. Another prediction that I haven’t found that he made explicitly is that there should be a range of heritable variation in nectary length — it could just be that that was so obvious in the collections he examined that it wasn’t necessary to state it.
Anyway, lovely as it is, a video of an insect with a remarkably long proboscis is not confirmation of Darwin’s theory. The key element of that theory is a description of a process which generates diversity over time in populations, which isn’t assessed by examining a single organism at a single moment in time.
(via Atheist Media Blog)