The ancestry of the long-lived / by Raymond Pearl and Ruth DeWitt Pearl.

  • Pearl, Raymond, 1879-1940.
Date:
1934
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: The ancestry of the long-lived / by Raymond Pearl and Ruth DeWitt Pearl. Source: Wellcome Collection.

    22/192 (page 4)
    4 ANCESTRY OF THE LONG-LIVED slightly over one female person out of the hundred of each starting together at birth is alive at age 92. The group of highest survivorship at that age (Norway) has over 1000 times as many male survivors at 92, and over 1500 times as many female survivors as the group of lowest survivorship (India). Furthermore, if we leave out India as a some¬ what special case, and take Italy for comparison with Norway, it is seen that the latter country has 9.2 times as many males alive at 92 years of age, and 12.2 times as many females. When the last two columns of the table are examined a still different state of affairs presents itself. The persons of any race or clime who live to age 92 show, as subgroups, extraordinarily little inter-group variability in their average total longevity [CML (92)]. Now it is evident that the immediate reason, things being as they are, why these extremely longevous sub-groups exhibit such small inter-group varia¬ tion is because age 92 is so near the upper limit of the human life span. In a manner of speaking they have no room in which tO' vary much. But this is only a statistical aspect of things as they are. Biologically the upper limit of the human life span is determined only by the inability of human beings, as now bred and environed, to live much more than 95 to 100 years.* There is no necessary theoretical or bio¬ logical reason why some human beings should not have their length of living so distributed that the inter-group variability in respect of CML (92) would be of the same order of magnitude as that in respect of CML (o) now is. There simply are not sufficient numbers of such people at the present time. Possibly at some future time there may be. Actually at the present time the inter-individual variability of persons living at ages of 90 and beyond is shown farther on in this study to be of the order of magnitude indicated by a coefficient of variation of less than 4 ± . i per cent. The relative inter-group variabilities shown by the data of the table are as follows, measured by the coefficients of variation, with India omitted in all cases for reasons indicated above. Male expectation of life at birth.. , Female expectation of life at birth,, Male per-ioo-born-survivorship at 92 = 8.64 % = 903% = 68.14 % * Cf. Pearl, R. Span of life and average duration of life. Natural History, Vol. 26, pp. 26-30, 1926.