378 



The Journal of Heredity 



lished the heritable nature of congenital 

 deafness* — Dr. Bell is now working on 

 the published history of the Hyde 

 Family in the United States, and 

 analyzing it from many points of view 

 to bring to light the ways in which 

 longevity is inherited. It is obvious 

 that this trait is a particularly easy one 

 for investigation, because we need to 

 know nothing more than the dates on 

 which an individual and his parents 

 were born and died. Certainly a gen- 

 ealogy that does not tell so much, must 

 be considered defective; and yet of the 

 8,000 or more persons listed in the Hyde 

 genealogy, there are less than 3,000 for 

 whom these data are complete. 



Longevity being due more to heredity 

 than to anything else, it is evident, as 

 Dr. Bell has clearly pointed out. that 

 it is a trait of which families may well 

 be proud, if it runs consistently in their 

 stock. And, as we eugenists try as far 

 as possible to put our knowledge to 

 practical use, he has also pointed out 

 that it is very desirable for a young 

 man or young woman to marry into a 

 family possessing that trait, since it is 

 a good indication of general soundness 

 of constitution and physical vigor. 

 Families in whose ancestry longevity is 

 a characteristic can well afford to make 

 the fact known and take pride in 

 alliance with other worthy families 

 similarly endowed. 



Such a mating, like with like, is 

 technically known to us as assortative. 

 It used to be supposed that people 

 tended to marry their ojjpositcs — the 

 blonde and the brunette, the short and 

 the tall. The use of exact methods in 

 eugenics has demonstrated that the 

 reverse is the case, and that for almost 

 every measurable trait there is distinct 

 evidence of assortative mating.'' That 

 such a fact is of great value to the race, 

 when the character involved is one of 

 so much importance as longevity, is 

 obvious, and the tendency should be 

 encouraged. Genealogy can give nuuli 

 help in this connection. 



There arc certain phases of the 

 always interesting problem of sex- 

 determination on which genealogy can 

 easily throw light. It has sometimes 

 been asserted that the age of the i^arents 

 influences the sex of the offspring. We 

 do not know that this is so, but with 

 the help of genealogy we might find out. 



Another question of great practical 

 importance, on which we seek informa- 

 tion, relates to the posterity of men of 

 genius. Is there any truth in the idea 

 that their mental activity tends to use 

 up some vital force, with the result that 

 they are either sterile or leave posterity 

 of mediocre quality? The idea does 

 not sound convincing, but we .shall not 

 dismiss it dogmatically; we shall appeal 

 to genealogy for data on which to dispose 

 of it definitely. Of course the alleged 

 fact here must not be confused with the 

 well-known fact of regression, fonnu- 

 lated as a mathematical law by Galton. 

 We know that, on the average, the 

 children of superior parents will tend 

 to be inferior to their parents, and the 

 children of parents who are below 

 normal will tend to be a little better 

 than their parents. This is due to the 

 vast bulk of their remote ancestry, 

 most of which is necessarily average or, 

 as the statistician puts it, mediocre. 

 The drag of this more remote heredity 

 tends to pull every child toward 

 mediocrity, or the mean, the average of 

 the race. I must emphasize the fact 

 that this is purely a statistical law, 

 applying only to a quantity of cases, 

 and is frequently untrue for indi\-idual 

 cases. 



The results of early as compared with 

 late marriage offer another big problem, 

 in the solution of which we need \-()ur 

 hcl]). 



That the first-born children are, on 

 the whole, inferior to the l^rothers or 

 sisters who come after theni has been 

 asserted in recent years, and the asser- 

 tion has been supported by a good deal 

 of evidence. It is highly important 

 that a much greater body of evidence 

 be brought together on this point, and 



" Bell, Alexander Graham. Memoir upon the Formation of a Deaf X'ariety of the Human Race. 

 Washinj^ton, D. C, .National Academy of Sciences, 1.S.S4. 



» For a sumrnary see Harris, J. Arthur. Assortative Mating in .Man. ]'oi>ular Science Monthly, 

 LXXX, No. 5, pp. 476-493, New York, May, 1912. 



