Richard Dawkins has a new book, in which he sets out to prove, once and for all, that evolution is a fact `in the same sense as it is a fact that Paris is in the northern hemisphere’, or, as he calls it, a Theorum.

Here he is talking about a prediction made by Darwin and Wallace after observing the striking length of the nectaries of Angraecum Sesquipedale (it’s an orchid ) that an insect capable of extending to such a length must exist. The insect was indeed discovered forty years later, and aptly baptized praedicta.

This little example gives the lie, yet again, to the allegation that evolutionary science cannot be predictive because it concerns past history

(The Greatest Show on Earth, Kindle location 718)

Two comments come to mind. First, this prediction, insightful as it is, has little to do with the core assertions of evolutionary science — that all species evolved from one another, and that this process is driven by random mutations and natural selection. Indeed, it seems to me that Darwin was not appealing to any of these ideas when he made it, but based it solely on the fact that the plant fertilizes via insect pollination and that the nectar serves to lure these insects. I don’t care or know much about creationists, but my guess is that this fact will be gladly adopted by the most diehard of this lot, since it perfectly fits their framework of design and purpose in Nature.

Second, when critics complain about the poor predictive power of evolutionary science, they mean I think falsifiable prediction. An assertion that an insect will be discovered at some unspecified time in the future is not falsifiable, because you can never go wrong. Either the insect is found, in which case you made a prediction that turned out to be true or the insect has not been found yet, but this does not serve to weaken the theory of evolution. Case in point: Angraecum longicalcar, a cousin of the A. Sesquipedale whose nectaries are too long even for the praedicta. The insect whose tongue is large enough to suck the nectar from the longicalcar was not found yet, but Dawkins is not a bit embarassed by this fact. On the contrary, he only mentions it as another manifestation of the predictive power of evolution.