CUMULATIVE EVIDENCE FOR EVOLUTION 



2. The king crab, Limulus, is more closely related to 

 scorpions and spiders than to any true crabs. 



3. The whales, whose affinities among mammals have long 

 been a problem, show an unmistakable affinity to the hoofed 

 mammals, especially to the swine. 



4. All Primates show closer affinity to one another than 

 to any other mammals. 



5. Similarly, all Carnivora are more like one another in 

 blood than they are like other mammals. 



When the system of classification based upon blood tests 

 is compared with that based upon homologies it is found 

 that the two corroborate each other in all essential respects. 

 Where the method of homology had left the affinities of an 

 animal somewhat doubtful, the blood test has been a valu- 

 able check upon earlier findings. Some relationships that 

 were only doubtfully hinted at by homology have been defi- 

 nitely confirmed by blood tests. 



One of the most conclusive evidences of the essential truth 

 of the concept of evolution is that two utterly difiFerent 

 methods of testing the relationships of animals should thus 

 be in close agreement. If the blood-test method had given a 

 different set of relationships than those indicated by homol- 

 ogy we should doubtless have lost confidence in the validity 

 of one or both methods, and our confidence in the principle 

 of evolution would be to some extent shaken. To the same 

 degree, then, that a disagreement in the results of the two 

 methods would have weakened our confidence in evolution 

 should not the close agreement of the two methods strengthen 

 our confidence in it? 



Another example of the way in which the evidences from 

 diverse fields of science converge upon one conclusion, and 

 only one, is to be found in the relationship of birds and rep- 

 tiles. Studies of the comparative anatomy of adult birds 



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