mammals with their protected young had developed, and 

 these evolved into numerous types of modern mammals, 

 including the ancestors of the horse, pig, and cattle during 

 the Eocene period starting 70 million years ago. During 

 this period primitive monkeys also first appeared, which 

 gave rise in the next period — the Oligocene, starting 40 

 million years ago — to a primitive tail-less ape living con- 

 temporaneously with the ancestors of modern dogs, cats 

 and bears. In the succeeding Miocene period, which began 

 25 million years ago, the primitive anthropoid ape called 

 Proconsul, which lived in central Africa, migrated into 

 Asia and Europe, and the number of man-like ape species 

 increased on into the Pliocene period (beginning 1 1 mil- 

 lion years ago) while the number of other mammalian 

 species declined — possibly because of the changed cli- 

 matic conditions over the Earth, which became more varied 

 during the Miocene period. Finally, in the most recent 

 Pleistocene period starting 1 million years ago, ape-like 

 animals developed intelligence enabling them to make 

 stone tools as weapons and for use in handling killed ani- 

 mals. These marked the transition to primitive man, who 

 probably originated in Africa and lived in forest and open 

 country. He spread outwards to Asia and Europe and was 

 able to thrive and evolve his intelligence and manual 

 skills through the cold periods of the Ice Age and the warm 

 interglacial periods — when other mammals were forced 

 to migrate away from the glaciated regions in Europe, 

 America, and India, or were rendered extinct by the hostile 

 climate. With the coming of the end of the last period of ice, 

 about 12,000 years ago, Man learned how to domesticate 

 certain animals and to cultivate certain plants for food 

 and other purposes. These advances in his evolution made 

 possible the growth of large human communities, which 



