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.