Influenza viruses, comets and the science of evolutionary trees

The study of phylogeny is becoming increasing scientific in that hypotheses can be tested quantitatively. We report a method of estimating the probabilities of obtaining a tree of a given length from nucleic acid sequence data. The method is applied to the hypothesis of Hoyle & Wickramasinghe that the earth is being continually bombarded by influenza (and other) viruses which originate from comets. A quantitative analysis of sequences from the H1 strain of human influenza viruses contradicts three versions of the Hoyle-Wickramasinghe model. One non-evolutionary version of their model has less than one chance in 10 66 of being correct. A version that allowed extraterrestrial evolution has less than one change in 10 6 of being correct. The sequence data is in agreement with the biological (evolutionary) model. The results are discussed from the aspect of the falsifiability of evolutionary theory.