204 Changing Human Nature 



are probably closely related as groups of hereditary charac- 

 ters. For example, both the head and the hand are probably 

 related in their development to the erect posture, as is the 

 development of the foot. Inguinal hernia (which is unknown 

 among the lower mammals) and the distinctive curvature 

 of the spine are also related to the erect posture. 



We have had impressed upon us the similarities between 

 man and other primates. It is well to recognize also the un- 

 derlying differences. The more important of these are shown 

 in the table on page 206, compiled from President Osborn's 



work. 



1 



Monkey Tails and Other Superfluities 



Because of the associations and prejudices which most of 

 us take on early in life, we almost inevitably consider the 

 presence of a tail in human beings either frivolously as a joke 

 or solemnly as a humiliation. But there are occasionally 

 human individuals (a very small fraction of the population, 

 to be sure) who have definite tails, though these are seldom 

 very long, and never active. Moreover, during a very early 

 stage in the development of the individual, the series of verte- 

 bras that make up the backbone extend beyond the limbs 

 into an unmistakable tail (Fig. 52). In most cases, these 

 terminal vertebras are absorbed so that at the time of birth 

 there remains no external indication of this structure. 



As we have seen, there are numerous other structures 

 and details which are taken by the biologists to indicate that 

 mankind in some remote past was different from the human 

 race of today (see pages 97 ff) . There is, for example, the 

 problem of the mammary gland. Linn^us established the 

 order of mammals to which he gave the name Primates, and 

 he distinguished it from the other mammals by the fact that 

 whereas in the lower orders there are several pairs of mam- 

 mary glands, in this order there is only one pair. But the 

 glands are present not only in the female, where their func- 

 tion is obvious, but also in the male, in a rudimentary state. 



