THE APPLICATION TO MAN 239 



in order to maintain the vigor and avoid the defects 

 of any line. In the case of mankind, consanguineous 

 marriage of various degrees has long been forbidden 

 by law or custom in many races, particularly among 

 the Jews, Mohammedans, Indians and Romans. On 

 the other hand, the Persians, Greeks, Phoenicians and 

 Arabs have freely practised inbreeding, while one of 

 the longest of known human pedigrees, a royal line 

 of Egypt, was notorious for close inbreeding, even to 

 the mating of brother and sister. 



There has been a greater degree of inbreeding in 

 the Puritan stock of New England than is commonly 

 realized. David Starr Jordan points out that a 

 child of to-day, supposing no inbreeding of relatives 

 had occurred, would have had in the time of William 

 the Conqueror, thirty generations ago, 8,598,094,592 

 living ancestors. If this theoretical supposition 

 were really so, it would seem quite possible for every 

 New Englander to-day to have had at least one an- 

 cestral representative who won glory under William. 



The difference between the unthinkable number 

 given above and the actual number of probable 

 ancestors alive thirty generations ago emphasizes 

 the fact that inbreeding must have occurred freely. 



There are, indeed, various well-known provisions 

 in nature to insure inbreeding. The majority of 

 plants are probably self-fertilized while hermaphro- 

 ditic animals, which sometimes at least are self- 

 fertilized particularly among the lower forms, are 

 very common. 



Nature has secured, on the other hand, often by 



