Published online by Cambridge University Press: 18 August 2016
According to Wallace and Weisman the duration of life in any organism is determined by natural selection. An organism lives so long as it is advantageous, not to itself, but to its species, that it should live. But it would be impossible for natural selection to determine the fit duration of life, as it would be impossible for it to fix any other character, unless that character were inherited. Accordingly the hypothesis above referred to supposes that duration of life is an inherited character. So far as we are aware, however, neither of the above-mentioned naturalists, nor any other investigators, have published researches bearing on the problem of whether duration of life is or is not inherited. We are accustomed to hear of a particular man that “he comes of a long-lived family”, but the quantitative measure of the inheritance of life's duration does not yet seem to have been determined. This absence of investigation appears the more remarkable as a knowledge of the magnitude of inheritance in this respect would, we should conceive, be of primary commercial importance in the consideration of life insurance and of annuities. The biological interest of the problem, as we have already noticed, is very great.
page 112 note * See Weismann, On Heredity, Essays I and II, and especially Professor Poulton's Note as to Wallace, p, 23, of first English edition.
page 115 note * Phil. Trans., vol. 192, p. 277.
page 115 note † Roy. Soc. Proc., vol. 62, pp. 397 and 400.
page 115 note ‡ This selective death-rate from the data for father and son must be interpreted in the sense indicated above. The drop from 80 to 65, say, per-cent is in itself a measure of the change of environment of the two generations.
page 116 note * The correlation on which this determination is based might be illusory, if families were reared under very individual environments; the correlation in duration of life of brothers, for example, might then be a result of their individual family environment. But the environment when we take comparatively homogeneous classes like the Peerage or Landed Gentry must be very similar, and we think this source of error, suggested to us by Professor Weldon, while very real, has been sufficiently provided against.
page 116 note † Not of course very largely, still, with the values given in the first series of fathers and sons, the correlation would be reduced about 0·86 to 0·9 of its value by the selection of fathers.
page 117 note * Phil. Trans., vol. 186, p. 406 and plate 16.
page 117 note † Roy. Soc. Proc., vol. 60, p. 480.
page 117 note ‡ Roy. Soc. Proc., vol. 62, p. 386.
page 121 note * Phil. Trans., A, vol. 186, p. 408, and Plate XVI.
page 122 note * This collection has already commenced, and we hope shortly to give more definite information on this point.
page 122 note † Wallace, loc. cit., supra.
page 124 note * “Contributions to the Mathematical Theory of Evolution. III, Regression, Heredity, and Panmixia”, Phil. Trans., A, vOI. 187, pp. 253-318.
page 126 note * In obtaining the formulae for prediction from the age at death of two relatives, certain assumptions have had to be made. Thus the correlation of ages of a man and his grandfather and of a man and his uncle at death, being at present unknown, were taken to be half the correlation of father and son. This cannot be far wrong, but the actual values ought to he found. We did not feel justified in assuming the variability of grandfathers, which must be less than that of fathers, or their mean age at death, which must be greater than that of fathers, in order to determine the probable age at death of a man from that, say, of his grandfather and father, which would be of much interest. We only wish t o draw attention to what we believe to be a new and important field of enquiry and to indicate the nature of its problems.