The Origin of Species and The Voyage of the 'Beagle'

Author Essay

Suppose we measure the power of a scientific theory as a ratio: how much it explains divided by how much it needs to assume in order to do that explaining. By this criterion, Darwin’s theory of evolution by natural selection is second to none. Think of what it explains -and I really mean explains in the fullest sense of the word: your existence and mine; the form, diversity, and apparently designed complexity and elegance of all living things, not only on this planet but probably wherever in the universe organized complexity may be found. The
explanatory work that the theory does, then – the numerator of the ratio – is immense. But the theory itself – the denominator – could hardly be smaller or more simple; you can write it out in a phrase: ‘Non-random survival of randomly varying hereditary elements.’ That isn’t quite how Darwin himself would have put it (he phrased it in terms of the survival and reproduction of individual organisms). But it captures the essence of his idea in a way that- I am convinced – he would recognize and, indeed, enjoy if he were alive today.