492 THE POPULAR SCIENCE MONTHLY 



matings, and in such a way that, on the average, similar individuals 

 tend to marry. 



These results will probably be received with much scepticism. The 

 " charm of disparity," the " selection of opposites," has been so long 

 asserted that the notion will not readily be given up. Concretions of 

 vague impressions compacted into popular superstition are not soon 

 broken up by the hammer of logical deduction from scientific measure- 

 ment. This scepticism of preconception can, however, be ignored; in 

 time it must give way to orderly arranged facts. Yet the scientist 

 should not forget that when cracked open, the nodules of popular be- 

 lief are often found to contain a scrap of truth — and in his turn should 

 avoid dogmatism. 



Purely biological phenomena are far more complex than the ma- 

 jority of naturalists have realized. When social factors are superim- 

 posed the difficulties of research become almost unsurmountable. Pear- 

 son has warned us that "in many factors there may actually be two 

 opposed currents, one giving a tendency for like to mate with like and 

 the other marked by the fascination of extremes." Goring's studies of 

 criminals vindicate one's a priori conviction that assortative mating 

 may be influenced by social conditions. Human society differs so pro- 

 foundly from place to place and time to time that, however great the 

 temptation to generalization may be, it would be folly to press the con- 

 clusions far beyond the data which they represent. 



Moreover, if the biometric results reviewed in the preceding pages 

 must be fitted post haste into some evolutionary scheme, or find an 

 immediate practical social application, each reader must be responsible 

 for his own. The difficulties of interpretation are even greater than the 

 dangers of generalization. To-day, an unfortunately insistent demand 

 that every datum must count for or against some current theory has 

 largely replaced the Darwinian spirit of collecting facts in the hope 

 that when sound and sufficiently numerous, reasonable theories may be 

 fitted to them. To-day " a fact is not a fact until it fits a theory." 

 Personally, I feel as thoroughly satisfied that the time is not yet ripe 

 for interpretation as I am completely convinced that in the differentia- 

 tion and painstaking measurement of the intensity of the individual 

 possible factors we have begun to move in the right direction in the 

 attack upon the phalanx of problems which we designate as organic 

 evolution. The immense value of these pioneer studies by Pearson and 

 his associates lies in the fact that they represent the definite and sub- 

 stantial beginning of quantitative research which is so large a part of 

 the solution of a problem. 



