We continue to look at Christoph Adami’s book, The Evolution of Biological Information. In his summary to his chapter on “Experiments in Evolution,”he offers a defense of evolution’s status as a scientific theory by arguing that it makes “qualitative and even quantitative predictions that can be tested by anyone.” In fact, he says that Darwin was able to immediately use his theory to make predictions.
Adami’s example is that of the orchid Angraecum sesquipedale. This orchid has an extremely long nectary, or spur, the place that contains nectar and that spreads pollen on any insect that drinks the nectar. Most pollinators have proboscises that are far too short to reach nectar. From this, Darwin concluded, “In Madagascar there must be moths with proboscises capable of extension to a length of ten to twelve inches.” Alfred Russel Wallace, co-discoverer of the principle of natural selection, agreed and suggested the moth in question was likely a sphinx moth, as they often had long proboscises, albeit none had been observed with one long enough. Such a moth would eventually be discovered, approximately forty years after Darwin’s prediction.
A Confirmed Prediction?
Is this an impressive example of Darwin’s theory making a confirmed prediction? What does the prediction even have to do with Dawin’s theory? Given an orchid with a long spur, the existence of a pollinator with a long proboscis is a pretty natural inference. That inference could be made whether one thinks the length of spurs is shaped by natural selection or a creator. The prediction does not seem to have anything to do with the theory.
Wallace was able to correctly predict that the moth would be a sphinx moth. But this was simply because other sphinx moths had long proboscises. It was therefore easily plausible that there might be one with an even longer one. His prediction does not require evolutionary theory.
Adami states that this prediction was made possible by “the law of co-evolution.” I, for one, have never heard of such a law. A Google search turns up a single page of results, none of which appear related to biology. “Co-evolution,” or “coevolution,” is a thing, of course. But not “law of co-evolution.”
Adami tries to use this example to bolster his claim that evolutionary theory makes testable predictions. But what he has actually done is taken a prediction that has nothing to do with evolution and attribute it to evolutionary theory.