Evolutionary Clock: Nonconstancy of Rate in Different Species

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Science  11 Aug 1972:
Vol. 177, Issue 4048, pp. 530-532
DOI: 10.1126/science.177.4048.530


By using various methods for comparing polypeptide sequences we find that the evolutionary divergence of rattlesnake cytochrome c from cytochromes c of species in other classes has been more rapid than that of cytochrome c of another reptile, the snapping turtle. This suggests that the evolutionary rate of change of cytochromes c is species-dependent as well as time-dependent.