FOSSIL PEDIGREES 111 



Ordovician, and Silurian rocks are extinct, whereas modern 

 types abound in Cretaceous and Tertiary rocks. Hence it is 

 claimed that the former must be vastly older than the latter. 

 But this argument gratuitously assumes the substantial per- 

 fection of the stone record of ancient life and unwarrantedly 

 excludes the possibility of a sudden impoverishment of the 

 world's flora and fauna as the result of a sweeping catastrophe, 

 of which our present species are the fortunate survivors. Now 

 the fact that certain floras and faunas skip entire systems of 

 rocks to reappear only in later formations is proof positive 

 that the record of ancient life is far from being complete, and 

 we have in the abundant fossil remains of tropical plants 

 and animals, found in what are now the frozen arctic regions, 

 unmistakable evidence of a sudden catastrophic change by 

 which a once genial climate "was abruptly terminated. For 

 carcasses of the Siberian elephants were frozen so suddenly 

 and so completely that the flesh has remained untainted." 

 (Dana.) Again, the mere jact of extinction tells us nothing 

 about the time of the extinction. For this we are obliged to 

 fall back on the index fossil whose inherent time-value is based 

 on the theory of evolution and not on stratigraphy. Hence 

 the argument from extinct species is not an independent 

 argument. 



To sum up, therefore, the aprioristic evolutional series of 

 fossils is not a genuine time-scale. The only safe criterion of 

 comparative age is that of stratigraphic superposition, and 

 this is inapplicable outside of limited local areas. ^ The index 

 fossil is a reliable basis for the chronological correlation of beds 

 only in case one is already convinced on other grounds of the 

 actuality of evolution, but for the unbiased inquirer it is 

 destitute of any inherent time-value. In other words, we can 

 no longer be sure that a given formation is old merely be- 

 cause it happens to contain Cambrian fossils, nor that a rock 

 is young merely because it chances to contain Tertiary fos- 



'"All that geology can prove," says Huxley, "is local order of suc- 

 cession." ("Discourses Biological and Geological," pp. 279-288.) 



