ZOOGENESIS 



in individuals, a group including forms of which the 

 average size is very small, and which have help- 

 less young. 



Among the birds the dominant types, most numer- 

 ous both in species and in individuals, are again those 

 of small size with helpless young. 



Here we seem to be confronted with a paradoxical 

 situation. For we find, in the animal world taken 

 as a whole, that where the greatest weakness lies 

 there also lies the greatest strength — evidenced by the 

 greatest degree of material success. Everywhere we 

 see as the dominant types of animal life, at least on 

 land, types with marked inherent weaknesses — small 

 feeble bodies and dependent helpless young — which 

 we might offhand assume would imperil their ex- 

 istence. 



But in all these types weakness of body and the 

 many liabilities resulting from the helpless young are 

 more than offset by the occurrence of more or less 

 manlike mental alertness and ingenuity. 



Do the physical liabilities give rise to the mental 

 alertness and ingenuity? Do the mental attributes 

 permit the existence of liabilities? Or are mental 

 alertness and physical liabilities both correlated in 

 some way with definite structural features? These 

 questions we shall answer later. 



From the physical viewpoint man is relatively one 

 of the least efficient of all living creatures. His feeble 

 body is no match for the powerful bodies of the great 

 grass-feeding mammals which in the relatively recent 

 past roamed all the open areas of the world and also 



[19] 



