the methods of death registration enable us to form an approximate estimate of the proportion of childless marriages among the whole population of somewhat mixed British race, with a high standard of living, we find that the proportion of marriages in which there are no surviving children at the father's death is about 16 per cent. With due allowance for the earlier death of the children and for the ignorance, in a certain proportion of cases, of those who filled in the death certificate, it is probable enough that this result is not really larger than the other. In any case there is an excess of sterility among the group of intellectually eminent men, this excess being the more marked when we remember that in very large majority they belong to a period when the artificial restraint of reproduction had scarcely begun to be widely practiced.
It is somewhat remarkable that, although the number of infertile marriages is so large, the average fertility of those marriages which were not barren is by no means small. We have fairly adequate information in the case of the marriages of 214 of these eminent men. I have not included those cases in which the national biographer is only able to say that there were 'at least' so many children, nor have I knowingly included any cases in which there were two or more marriages. Whether the number of children represents gross or net fertility, it is, unfortunately, in a very large proportion of instances, quite impossible to say. It is probable that in a large proportion of cases only the net fertility, i. e., the number of children who survived infancy and childhood, has been recorded. It is, therefore, the more remarkable that the average number of children in these 214 fertile families is 5.45. Thus, although our data are probably imperfect, they show that the fertile marriages of British men of genius have produced families which contain on the average one child more than the fertile marriages of ordinary people of the same race during the nineteenth century; in New Zealand the average number of children left by fathers of families (whether as the result of one or more marriages) dying between the ages of twenty-five and sixty-five, is 4.81, which indicates a much larger gross fertility. It must, of course, be remembered, on the other hand, that the eminent men in our group lived to a very high average age, and it is obvious that.men who live to an advanced age will have a better chance of leaving large families than those who die young.[1] This consideration somewhat diminishes our estimate of the fertility shown by British men of genius, while, if we take barren marriages into
- ↑ Even apart from this, there appears to be a connection between longevity and fecundity; see M. Beeton and Karl Pearson, 'On the Correlation between Duration of Life and the Number of Offspring,' a paper presented to the Royal Society of London June 14. 1900.
