In a paper which was read before the Institute of Actuaries on the 31st May, 1852, “On the Uniform Action of the Human Will, as exhibited by its Mean Results in Social Statistics,” I drew attention to the remarkable regularity with which marriages are contracted in any country, and the very small limits of difference from the average number which appear from year to year. The observations made by M. Quetelet in Belgium, from 1825 to 1845, showed that the extreme difference in the total number of marriages was little more than half the difference of the extremes in the number of deaths in the same period. Such a conclusion seemed to imply that the subject was worthy of more research. If the law of mortality can be so accurately defined at different ages, that pecuniary interests, amounting to some hundreds of millions sterling, can be valued and adjusted with the greatest nicety, it is reasonable to conclude that the labour of a statistical inquiry into the proportion of marriages at different ages would be rewarded with the discovery of some equally defined law, since the variations from year to year in a given number of facts appear, from a large number of observations, to be even less than in the former case. It is true that, as human life must fail at some time, from the natural decay of the powers of life, every interval of age after man has once attained maturity may be expected, under ordinary circumstances, to show a steady and progressive increase in the liability to disease and death. On the other hand, it may be, argued that marriage is the exercise of the free will of man—that consequently, it does not depend on the age or period of life, but on the arbitrary exertion of those feelings or mental and moral qualities which are not subject to natural laws, or at least not to such laws as we are able to express numerically in the same manner we can the law of mortality in any given population. If we consider, however, marriage as, in one sense, the natural provision for the preservation or increase of the species, and the counteraction to the law of mortality by which the species would perish, we should not be surprised to find that, however imperceptibly to individuals, there is a tendency to obey some unknown law of nature which at the period of maturity would lead to the maximum of marriages, and gradually diminish with age in the same manner as the tendency to disease and death increases with age. The motives and caprices of individuals would only have the same effect on the general results which the different habits of individuals may have in increasing or diminishing the rate of mortality. Accordingly, M. Quetelet, in a comparison of the number of marriages in Belgium for each five years of age after 21, for both sexes, for a period of five years consecutively, showed that the average results in each period scarcely differed at all from year to year. The table is so remarkable, that I have reduced the proportion to 100 of the total marriages in each year, and present it to show the small differences which will then be seen to prevail.
Repeatability of endocrine traits and dominance rank in female guinea pigs
