over a period of time, the rabbit's body will form specific antibodies that will 

 produce a cloudiness if mixed with human blood. The antibody is said to 

 "precipitate" the specific human protein, but the rabbit's serum will not 

 react in this way with the blood of a hen or a sheep. But it will precipitate — 

 somewhat — if mixed with monkey blood. And it will precipitate more if mixed 

 with ape blood (see page 240). 



These and similar experiments carried on over many years show that the 

 structural resemblances between animals which we class as "related" have their 

 parallel in chemical resemblances. The blood of man is more like that of an 

 ape than it is like the blood of a monkey, and it is more like the blood of a 

 monkey than it is like that of a lemur. 



In structure, in the common functions, in development, in chemical pecu- 

 liarities, and in genetic behavior man is like other organisms. And the degree 

 of resemblance, as well as the degrees of difference, warrants us in thinking that 

 man is subject to the same forces or influences as have brought about trans- 

 formations in other species. 



Evolution and Man At the close of the last century thinking people 

 were discussing the evolution theory as applied to man. Many who were 

 willing to assume that evolution had taken place among plants and lower 

 animals hesitated to accept the same explanation for the appearance of man 

 upon earth. One of the strongest arguments urged against the theory was the 

 fact that it had been impossible to produce a complete record of a graded 

 series connecting men of today with his supposed nonhuman or prehuman 

 ancestors. 



This argument of the "missing link" carried a great deal of weight. For 

 most people do not appreciate how unHkely it would be for a complete series 

 of specimens to be preserved through the far-reaching changes which the 

 earth itself has undergone. Of the millions of human beings and other verte- 

 brates that die in a given region during a century, how many skeletons are 

 Ukely to remain sufficiently intact to be recognized from ten to fifty thou- 

 sand years later? From a scientific point of view, it would be sufficient if the 

 scattered pieces found at widely different levels (geological ages) did actually 

 fit in with a supposed series. 



The few bones found in Java in the early eighteen-nineties by the Dutch 

 army surgeon Eugene Dubois (1858-1940) fit into such a series in a very 

 satisfactory way. The type of animal to which these bones belong was named 

 Pithecanthropus erectus, and probably represents a "missing link." This animal 

 had among his contemporaries a form of elephant, rhinoceros, Indian hip- 

 popotamus, tapir, hyena, a deer, and an animal somewhere between a tiger 

 and a lion. The climate and vegetation were similar in many ways to those 

 we now find in southern India and the islands of the region. 



A later discovery of ancient remains in Sussex (England) seems to point 



515 



