Simplistic combinatorial analyses are an honoured tradition in anti-evolutionary circles. Hoyle’s is the archetype of the combinatorial approach, and he gets a whole fallacy named after him for his trouble. The approach will be familiar – a string of length n composed of v different kinds of subunit is one point in a permutation space containing vn points in total. The chance of hitting any given sequence in one step, such as the one you have selected as ‘target’, is the reciprocal of that number. Exponentiation being the powerful tool it is, it takes only a little work with a calculator to assess the permutations available to the biological polymers DNA and protein and come up with some implausibly large numbers and conclude that Life – and, if you are feeling bold, evolution – is impossible.
Dryden, Thomson and White of Edinburgh University’s Chemistry department argue in this 2008 paper that not only is the combinatorial space of the canonical 20 L-acids much smaller than simplistically assumed, but more surprisingly, that it is sufficiently small to have been explored completely during the history of life on earth. Continue reading