Changes in the Fertility Span of Man

BRIEF PROPOSAL CHANGES IN THE FERTILITY SPAN OF MAN U. M. COWGILL* Some data are presented that suggest that the fertility span of man is increasing . The age of onset of menarche is becoming earlier and menopause is apparently beginning later. Some suggestions are made concerning possible restraining mechanisms and how they might operate so. that there is some control of the increased reproductive ability of the population. There are some aspects of the population explosion problem that appear to be poorly understood, or at least rarely discussed. One of these is the apparently steady increase in the fertility span of women. The age of onset of menarche has been declining since about 1840 [I]. In Norway, for example, the age of onset was about 17.1 years in the middle of the nineteenth century while now it is about 13.3 years. Around the turn of the century in the United States, it was about 14.2 years, while presently it is about 12.7 years. Frisch and Revelle [2] have proposed a hypothesis that a critical body weight may trigger the onset of menarche. If such were the case, the steady decline in age of onset might be explained . The age of onset of menopause is advancing. In 1918 [3] the mean menopause age was 47.1 years in the United States, but by 1962 [4] it had risen to 49.7 years. Thus, it would appear that part of the reason for the population explosion is the increasing fertility span of women. Historically, little is known about this problem. Hopkins [5], in his study of the age of Roman girls at marriage, presents data that at least are suggestive that the age of onset of menarche at that period was about thirteen-plus years. Amundsen and Diers [6], in their study of the age of onset of menarche in classical Rome and Greece, suggest that typically it occurred in the fourteenth year of life. Medical sources for this period suggest a modal age of thirteen to fourteen years. Nothing is known about this aspect of human fertility from Roman times until that period when churches began to keep records. In England from 1538 to sometime in the early eighteenth century [7-9], the age of marriage of both men and women advanced steadily. This was not an economic situation, as it was noted in the aristocracy and poor alike. Since economics may be ruled out as a factor in bringing about late marriage, it may be suggested that the advancing age of marriage might be a reflection of an advance in the age of puberty. During this period the size of die family decreased as the centuries proceeded. In York, England [10], 30 percent of the women over the age of forty were still bearing •Department of Biology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213. Perspectives in Biology and Medicine · Autumn 1971 | 141 children. It may be suggested that for this period late menarche was related to late menopause. Amundsen and Diers [11], in their study of the age of menopause in classical Greece and Rome, found that it occurred in the age range of forty to fifty, with a maximum of sixty years cited. Exceptionally early menopause , below the age of forty, appeared to be related to obesity. Presently, it would appear that early menarche is related to late menopause. In an attempt to determine whether an earlier age of onset of menarche is exerting an effect on total births in the world, a comparison was made between the available data from the period 1936-1949 [12] and those of die period 19551964 [13]. Though such material on the contribution to births made by adolescent and near-menopausal and menopausal age groups is scanty for the world, the data are shown in table 1. For each country, the available years in each age group were totaled and averaged. A percentage of the contribution of a given age group was calculated on the basis of total births for that country. During the two time periods compared, a few countries, namely Egypt, Algeria, Japan, Thailand, Mexico, and France, show a decline in the contribution to births in all age...