THE HELIX OF HISTORY 37 



and social development increases until the maximum is 

 reached. For most of the cycles discussed by Petrie, the 

 migration of a new stock appears to be a historical fact. The 

 dynastic people of Egypt, for instance, initiated Petrie's 

 fourth cycle, in which the peak \\a.s reached in the Fourth 

 Dynasty; people from the south, that of the Twelfth Dynasty; 

 the Hyksos invasion and the people of Thebes represent the 

 new blood for the New Kingdom cycle; the Doric invasion of 

 Greece initiated the classical cycle; and the influx of peoples 

 into the Roman Empire, the medieval cycle. 



The origin of cycles is discussed in a very interesting article 

 by O. G. S. Crawford.* Starting ^vith Petrie's idea that the 

 development of a new phase of civilization depends upon the 

 crossing of two stocks having their ow^n cultures, Crawford 

 pursues a biological analogy, comparing Petrie's different 

 stocks with different varieties of animals and concluding with 

 a generalization that each phase of civilization has a life of 

 its own and may be regarded as if it were a species composed 

 of living creatures. Thus the life of each phase corresponds 

 to the life of a species as a whole; the units composing the 

 phases at any moment of history correspond to the individ- 

 uals composing the species; and a phase, therefore, is born 

 and passes through maturity to decline and extinction, just as 

 does an individual. The idea is not new. Crawford quotes 

 Sir Arthur Keith, ^vho says: "The resemblance between the 

 body physiological and the body politic is more than an 

 analogy; it is a reality." f 



Just as a multicellular organism evolves from a single cell, 

 so the cultural community has evolved from free-roving in- 

 dividuals or small groups, this occurring, as has already been 

 pointed out, wdth the introduction of agriculture, -when the 

 nomads settled at one point and founded commimities. This 

 very operation can be observed occurring today, -^vhen the 



* O. G. S. Crawford, "Historical Cycles," Antiquity, V, 5 (1931). 

 fSir Arthur Keith, Concerning Man's Origin, New York, G. P. 

 Putnam's Sons, 1928. 



