60 THE LESSON OF EVOLUTION 



it is not until we reach the upper Pliocene that we 

 find complicated branching antlers. 



Dogs, cats, oxen, and the goat are first known 

 in the Pliocene. The sheep is of a very late origin, 

 and is hardly known in the fossil condition. Pithe- 

 canthropus erectus, of the pliocene of Java, was a 

 form intermediate between man and the apes 

 (gibbon?). It was an ape-like man which walked 

 erect. But there is not much difference in structure 

 between man and the higher apes. The bones and 

 muscles in both are the same, the differences between 

 them being chiefly due to adaptations necessary to 

 enable man to stand upright, and to use his legs 

 alone for locomotion. Man, like the apes, has 

 several vestigial organs which are of no use to 

 him, but which are well-developed and useful in 

 other animals. Among these are the remains of a 

 third eye-lid, as well as muscles for moving the ears 

 and the tail. Several other muscles, which are 

 always found in the lower animals, but which are 

 generally absent in man, are occasionally developed 

 in him ; and it is chiefly the presence of these ves- 

 tigial and useless structures which has convinced 

 naturalists that man has a common origin with other 

 mammals. 



It is a mistake to think that man was the last 

 species of mammal to appear on the earth. He 

 certainly dates from the Pliocene ; while several 

 animals, including the sheep, are not known to be 

 older than the Pleistocene. 



The oldest know y n human skeletons are those of 

 the Neanderthal and Spy caverns. They belong to 



