FURTHER EVIDENCE OF NATURAL SELECTION 
IN MAN. 
By ETHEL M. ELDERTON, Galton Research Fellow, 
AND KARL PEARSON, F.R.S. 
(1) The second author of the present paper writing in 1894 a commentary on 
the statement that " no man, as far as we know, has ever seen natural selection at 
work," remarked : " Every man who has lived through a hard winter, every man 
who has examined a mortality table, every man who has studied the history of 
nations has probably seen natural selection at work*." The emphasis is here to 
be laid on the word " probably," because the seeing depends on the power and 
validity of the scientific means adopted to analyse the observed facts. In a paper 
communicated by the same author to the Royal Society in June 1912f, it was 
shown from the Registrar-General's series of ten yearly life-tables that when 
allowance was made for change of environment in the course of the fifty years a 
very high association existed between the deaths in the first year of life and 
the deaths in childhood (1 to 5 years). This association was such that if the 
infantile deathrate increased by 10°/^ the child deathrate decreased by 5'S°/^ in 
males, while in females the fall in the child deathrate was almost l7o for f-very 
rise of 1°/^ in the infantile deathrate. The method of investigating by life-tables 
could not be extended beyond 1900, because the life-tables for the next ten 
years (1901-1910) were not then out, and indeed have only just appeared 
(December 1914). While the infantile deathrate as shown from the life-tables 
had risen from 1871-1900, the child deathrate had fallen for the same period. 
During the next decade 1900-1910 both deathrates have fallen together; such 
a secular change does not in any way modify the argument of the paper, which 
lies in the statement that whether two deathrates rise together or rise and fall 
simultaneously we can draw no inferences at all, until they have been connected for 
secular change. Most economic, demographic and physical variates are changing 
continuously with time, and no comparison of time graphs or calculation of 
correlations will demonstrate of necessity anything but spurious association, until 
* The Chances of Death and other Studies in Evolution, Vol. i. p. 166. 
t "The Intensity of Natural Selection in Man." R. S. Proc. B. Vol. 85, pp. 469—476. 
