602 POPULAR SCIENCE MONTHLY. 



this distribution seems to indicate that the mothers of persons of intel- 

 lectual ability are predominantly at the period of greatest vigor and 

 complete sexual maturity when they produce their distinguished chil- 

 dren. , Notwithstanding the tendency of first-born children to show 

 intellectual ability, none of the mothers are under 21. 



It may be noted that in at lea«t 36 of the 276 cases in which we 

 have details of the family history (or in about 13 per cent.) the mother 

 was a second or third wife. In at least 6 cases the father was a second 

 husband. 



It would have been instructive to compare the ages of the parents 

 and to ascertain the degree of disparity. I have only been able to do 

 this in 34 cases. There is a marked tendency to disparity which ranges 

 up to 49 years.* Whatever may be the normal amount of disparity 

 between the ages of parents, it certainly tends to range chiefly below 4 

 years, but in this group only 8 cases (t. c, in the proportion of about 

 23 per cent.) show less disparity than 4 years; the majority range be- 

 tween 4 and 8 years, and as many as 8 (i. e., in the proportion of over 22 

 per cent.) show a greater disparity than 10 years.f In 6 out of the 34 

 cases the mother was older than the father. In a considerable propor- 

 tion of cases both parents were elderly. 



On the whole it would appear, so far as the evidence goes, that the 

 fathers of our eminent persons have been predominantly middle-aged 

 and to a marked extent elderly at the time of the distinguished child's 

 birth; while the mothers have been predominantly at the period of 

 greatest vigor and maturity, and to a somewhat unusual extent elderly. 

 There has certainly been a notable deficiency of young fathers, and, still 

 more notably, of young mothers. 



Our data at this point are too few to be very decisive, but, so far as 

 they indicate anything, they enable us once again to bring men of 

 'genius' into line with the other mentally abnormal classes. The late 

 Dr. Langdon Down (who at my suggestion investigated the point some 

 twelve years ago) found that in the case of the parents of idiots there 

 was a disparity of more than ten years in 23 per cent, cases, almost the 

 same proportion as we have found in the parents of persons of intel- 

 lectual ability. Among criminals also inequality of age in the parents, 

 as well as elderly age of both parents, has been found by Marro to be 

 more common than among the normal population. Marro (in his 'Carat- 



*This very exceptional case was that of the father (an eminent bishop) of 

 Charles Leslie, the nonjuring divine. In this case the father was 79, the 

 mother 30. 



tin Hungary, as a table given by Korosi shows, if we take men at ages be- 

 tween 26 and 30, covering the most frequent normal age of marriage, in only 3 

 per cent, cases is the discrepancy of age as much as ten years. The disparity, of 

 course, tends to increase with the man's higher age at marriage. 



