38o THE POPULAR SCIE^iCU MONTHLY. 



unimpeded ratio at which ancestors multiply, they would amount in 

 the thirty-second generation to 4,294,767,296 ; and, reckoning for all 

 the checks to this ratio through the blending of lines of ancestry, they 

 must be reasonably estimated at the entire population of the globe — 

 as high, in fact, as they can possibly go. The CaflFre and the Hotten- 

 tot, the Japanese and the Chinese, are doubtless all of them the reader's 

 thirty-second cousins, or nearer. 



There is a tendency from many causes for ancestry to diverge and 

 spread itself over an ever-widening area ; there is a struggle of the 

 lines to part until universality has been reached, and every human 

 being has come into the succession. Even where a tribal or religious 

 custom mostly confines the marriages of the men in a community to 

 the women of the same community, there are sure to be many excep- 

 tions. Jews sometimes marry Gentiles, and set the barrier that 

 interposed between them at defiance. Boaz married Ruth, and she 

 brought into Judah blood mingled of all Moab. When the Quakers 

 made it a rigorous rule that members of the society should marry 

 only with members, gates were hung in the hedge, and the fence 

 itself was often broken through. Proselytes were brought in from 

 the outside ; members married non-members at the cost of excom- 

 munication. The law itself had eventually to be abrogated. 



The tendency to avoid kinship in marriage has helped to increase 

 the divergence of ancestral lines. While a large proportion of the 

 marriages consummated are between persons living in the same 

 district, the population of the district itself is continually undergoing 

 modification — one stream flowing in, another flowing out. No use 

 has been made in this argument of the existence of illegitimacy, and 

 the boundless license of many periods of our national history. Yet 

 doubtless moral transgression has greatly widened the area of rela- 

 tionship, and mingled in an indistinguishable mass the offspring of the 

 rich and poor. 



Hitherto we have been looking backward at the historical multi- 

 plication of the ancestors of persons now living. If we reverse the 

 process, and apply the law of multiplication to the future, the result 

 is equally startling. The average number of children may be reck- 

 oned on a moderate computation at two for every household. Ac- 

 cording to this average, a man who leaves permanent posterity be- 

 hind him has the number of his descendants doubled every generation. 

 The two children are followed by four grandchildren ; the four grand- 

 children by eight great-grandchildren. At the twenty-sixth genera- 

 tion the number has swelled to 67,006,624. A few more generations 

 would render them equal to the total number of the inhabitants of 

 the globe. So that, if one could rise from the grave at a period no 

 further removed from us in the future than the Conquest in the past, 

 every person he met in the land, man, woman, or child, if not a mere 

 visitor or recent immigrant, would be one of his descendants. Every 



