194 Changing Human Nature 



methods of analysis in both cases. That is, whatever value 

 his technique may have must be applied without preju- 

 dice as to the emotional associations that the material in hand 

 may carry. The chemist would also apply the same meth- 

 ods to determine the composition of a given bone without 

 prejudice as to whether it was the bone of a fish or of a 

 human being, the bone of a beggar or of a bishop. It is in 

 the same way that the zoologist applies his principles of classi- 

 fication and analysis to the samples of life which come to his 

 attention. When he comes to classify the mammals he in- 

 cludes among them men and mice as well as elephants and 

 whales. It is impossible to define our notion of 'mammal in 

 a way that will exclude man and yet include all the others. 

 Here is a class of backboned animals in which the skin cover- 

 ing is typically hairy; in which the blood is maintained at 

 a fairly constant temperature; in which the jaws are enclosed 

 by flesh and skin and carry enameled teeth in distinct sock- 

 ets; in which the fertilized ^%^ hatches into a formed young 

 within the womb of the mother; in which certain skin glands 

 produce a characteristic nutrient fluid used by the young; 

 in which the two pairs of limbs are typically provided with 

 five digits. 



If we consider the various orders of mammals we are 

 confronted with the problem of either placing man in an 

 order by himself or of combining him with the apes and 

 monkeys, into the order of primates. Again it is impossible 

 to define primates in a way that will exclude man but include 

 all the other mammals that properly belong in this order 

 (see page 75). In other words, we are forced to define 

 man as a kind of vertebrate, a kind of mammal, a kind 

 of primate. 



In tracing the ancient history of different classes of ani- 

 mals, the paleontologist is obliged to depend entirely upon 

 skeletal structures, since it is very rarely that anything more is 

 available for his study. Basing his judgments on a com- 

 parison of the various bones and of the teeth, he traces 

 through the fossils lines of descent and family trees. On 



