448 ZOOLOGY. 



their habits of life are interesting and suggestive in a high 

 degree, when we consider their possible relation to the human 

 species. In physical structure man differs less from the gorilla 

 and the chimpanzee than these from the monkeys of South 

 America. Man is the only primate native to this country, and 

 doubtless man came to America from Asia. 



453. Additional Notes on the Habits of Mammals. We 

 have seen that mammals have succeeded in occupying in over- 

 whelming numbers the land, in much less degree the water, and 

 least of all the air. We have classified them as insectivorous 

 (moles, ant-eaters, and bats) ; carnivorous, as the beasts of 

 prey; herbivorous, as the hoofed animals, rodents, and kan- 

 garoo; or omnivorous, as the pigs and man. They are very 

 versatile and have dominated the earth since the tertiary 

 epoch when they supplanted the immense reptiles of the earlier 

 ages. One of the most noteworthy facts in connection with 

 the group is the degree of care given to the young by the par- 

 ents, especially the mother. This is true not merely in gesta- 

 tion but after birth in the attendance of the mother to the 

 needs of the young, both in supplying food and in protecting 

 from danger. It must be remembered that this is done at the 

 expense of the parent's safety. It means that the species may 

 be kept alive by the birth of a smaller number of young, be- 

 cause more will reach maturity than if left early to shift for 

 themselves; and, further, that a higher development of the 

 young becomes possible owing to the increased length of youth. 

 The degree of development at birth is quite variable. In a 

 general way it is less in the case of those whose parents can 

 best protect the helpless young. For example the young of the 

 Carnivora and of the Primates are much less able to take care 

 of themselves at birth than the young of the Herbivora. Many 

 biologists have called attention to the fact that the greater care 

 of the young implies higher instincts and intelligence on the 

 part of the parent. This is subject to the action of natural 

 selection as an advantageous characteristic. In turn a longer 

 youth or period of development is demanded for the maturing 



