Table 2 Probability that the expression context conservation scores in different classes of orthologs and random non-orthologous gene pairs were drawn from the same distribution (see histograms in Fig. 2; Pvalues, Student's t-test; the distributions are normal according to a Shapiro-Wilk test, P < 1·10^{-4}). The expression context data is combined over all species comparisons: 1-1 orthologs (n = 10303) all X-X orthologs (n = 27147) most conserved X-X orthologs (n = 5180) less conserved X-X orthologs (n = 21967) random non-orthologous gene pairs (n = 6000).