Rate of Information Acquisition by a Species subjected to Natural Selection

David J C MacKay

At what rate, in bits per generation, can the blind watchmaker cram information into a species by natural selection? And what is the maximum mutation rate that a species can withstand? We study a simple model of a reproducing population of N individuals with a genome of size G bits; natural selection selects the N fittest children at each generation, variation among the children being produced by mutation or by recombination. We find striking differences between these two cases: if variation is produced by mutation, then the maximum rate of information gain by an entire population is of order 1 bit per generation, whereas if variation is created by recombination, information can be gained at a rate proportional to \sqrt{G}, the square root of the size of the genome. Furthermore, the maximum mutation rate that can be tolerated by a species that has recombination is greater than the maximum mutation rate tolerated by a non-sexual species by a factor of order \sqrt{G}.

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