488 THE POPULAR SCIENCE MONTHLY 



that they differ at all. The close agreement with stature, forearm, span 

 and other physical characteristics is clear. 



A criticism which may occur to the reader is that these resemblances 

 are purely spurious, and due to the fact that husband and wife are not 

 likely to be buried in the same ground unless they die within a short 

 period of each other. This is precisely what would occur in districts 

 with a shifting population. This very difficulty was anticipated. All 

 urban churchyards were excluded because of the heterogeneous and 

 transitory nature of the population. " In most rural districts, on the 

 other hand, with a stable population, there is a very strong feeling — 

 amounting in the case of the Yorkshire Dales almost to a superstition — 

 that husband and wife must share the same grave." In view of the 

 careful selection of localities and the agreement of results secured from 

 Quaker archives with those from the gravestones, it seems clear that the 

 resemblance can not be dismissed as purely spurious. 



Duration of life is doubtless dependent upon environment as well as 

 upon constitution. Slight differences in the healthfulness of the several 

 parishes of a district might promote or oppose fullness of years in men 

 and women alike. If this were true, the lumping together of the 

 records from a number of churchyards would result in a correlation for 

 duration of life, whether there be any real assortative mating or not. 

 If this criticism be valid, random pairs of husbands and wives from the 

 same parishes lumped together to form a table for the whole district, 

 should show correlations as high as those for actual married pairs. The 

 correlation really found was sensibly zero, demonstrating that local en- 

 vironmental conditions can not explain the results. 



But within the same general environment, members of a family are 

 exposed to a set of conditions peculiar to themselves. In a city block or 

 country parish food, temperance, sanitation, risk of zymotic disease, and 

 physical and mental habits differ greatly from family to family. In 

 addition to the physical and social environment common to man and 

 wife, there is also the fact that the death of one member of the pair has a 

 profound effect on the other. Financial and associated domestic changes 

 are often due directly to this cause, to say nothing of the overstrain of 

 care during long illness or the shock of sudden death. May not the 

 similarity in the duration of life of husband and wife be a consequence 

 of domestic environment? This point was investigated by methods 

 rather too complicated for explanation here, but which indicate that the 

 sameness of home conditions can not account for the relationship. 



Until further evidence is available, we must, therefore, conclude 

 that there is a real, though assuredly unconscious and quite indirect, 

 assortative mating for duration of life. Nor is this to be marvelled at, 

 considering the results already noted for normal and especially for 

 abnormal bodily characters. 



