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 valuable check upon earlier findings. Some relationships that were only doubtfully hinted at by homology have been definitely confirmed by blood tests.
One of the most conclusive evidences of the essential truth of the concept of evolution is that two utterly different 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 homology 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 reptiles. Studies of the comparative anatomy of adult birds
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