highly significantP < 10 −21
The rate of dS and dN substitutions between BMPR1BBY and BMPR1BB is 0.12 and 0.07, respectively, yielding a dN/dS ratio of 0.58, a dramatic and highly significant ( P < 10 −21 ) increase compared with dN/dS ratios of 0.01 to 0.02 in other branches of the tree ( Fig. 2 B and SI Appendix , Fig.