GEOLOGICAL HISTORY OF THE PRIMATES 597 



(Fissipedia), considered as a whole, constitute a fairly straight- 

 forward story, and are in obvious congruity with other geological 

 facts. With the monkeys and apes it is quite otherwise. The 

 attempt to unravel the history of the monkeys immediately 

 involves the investigator in some of the most vexed problems 

 of geological and geographical distribution, and in all manner 

 of cognate questions — problems of parallelism in evolution, 

 the rising and sinking of continents, the indirect implications 

 of other fossils, and the soundness or otherwise of our usual 

 criteria of mammalian classification. 



We have, therefore, to consider the position occupied by 

 the Primates in the history of the higher or placental mammals. 

 The subject is intimately bound up with certain problems of 

 geographical distribution. At the present day, the most 

 striking feature of the mammalian faunae of all the continents, 

 other than Australia, is their uniformity. There are great 

 cats all over Africa, Asia, and both Americas. The dog-tribe 

 are notoriously cosmopolitan. There are elephants in Africa 

 and in Asia ; and within the human period there have been 

 elephants of one kind or another all over the Western Hemi- 

 sphere as well. There are swine in Eurasia, swine in Africa, 

 and swine in Brazil. There is a tapir in Indonesia, and another 

 tapir in South America. There are monkeys in the jungles of 

 Africa, in the jungles of India, and in the jungles of tropical 

 America. There are hosts of allied groups of rodents all over 

 the world. The list of such cases could be extended indefinitelyi 

 It is true that there are exceptions. There are no deer and no 

 bears in Africa south of the Sahara. There are no civets 

 anywhere in the Western Hemisphere. One great group of 

 edentates is purely American. But these exceptions are few. 

 They are so few that they serve only to emphasise that general 

 uniformity which we encounter all round the world, save only 

 in Australia. The great orders of the Placentaiia are inter- 

 mingled nearly everywhere. Even granted that they have been 

 evolved in isolated areas in the past, it might appear that they 

 are now inextricably mixed. Yet geology does enable us largely 

 to extricate them from the apparently hopeless confusion. 

 Geology tells a beautifully simple, albeit a highly dramatic, 

 story of the presence of the great Felidse, the Canidae, the deer, 

 the tapirs, and the swine that we find in South America. But 

 it leaves us utterly puzzled about the teeming hordes of Ameri- 

 can monkeys. At first sight, nothing appears more natural 

 than the presence of monkeys in forests which harbour also 

 cats, dogs, deer, swine, and other mammals familiar to us in 

 the Eastern Hemisphere. But, as will be seen, the American 

 monkeys have quite a different history. 



At the present day the continents of what we may call the 



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