EVOLUTION OF PHYSICAL CHAEACTEES 369 



naturally less resistent to cold than the latter. In the broad and 

 rapid survey that we shall make these comphcations can be 

 disregarded ; the existence of tradition does not introduce, 

 so far as physical characters are concerned, that peculiar com- 

 plication which is the cause of much difficulty when we come to 

 deal with mental characters — namely, the combination of what is 

 acquired through tradition with the underlying character itself 

 in such a way that the manifestation of the character is connected 

 in a varying degree with its innate strength. We shall thus, 

 when dealing with mental characters, have to attempt to strip 

 off the acquirements. When dealing with physical characters 

 we can always get down to the character at once. There is no 

 difficulty in separating the arm from the tool which it employs, 

 and we thus get directly at the character which has developed as 

 the result of the influence of certain stimuli upon a given pre- 

 disposition. It is, on the other hand, difficult to separate the 

 intellectual characters from all those traditional elements which 

 combine with them in their outward manifestations — to measure, 

 for example, the strength of the instinct of curiosity, which 

 involves discounting all those elements in the tradition which 

 may inhibit or emphasize its expression. 



With regard to the strength of selection there is no exact know- 

 ledge, with the exception of some work which has been done upon 

 statistics for modern communities. The occurrence of selection 

 in the past is in fact merely a deduction from what we know 

 regarding innate predispositions and regarding elimination and 

 differential fertility. It has been shown, however, that lethal 

 selection does occur at the present day. Professor Karl Pearson 

 has calculated that selection accounts for a very large percentage — 

 perhaps 60 per cent. — of the deaths at the present day,^ and 

 Mr. Snow, summing up the results of an inquiry into this subject, 

 states that ' natural selection in the form of a selective death- 

 rate, is strongly operative in man in the early years of life '.^ 

 As it is universally agreed that, if anything, the intensity of natural 

 selection has decreased with civilization, we may take it as certain 

 that it was operative to as great, or to a greater, extent during 



1 Pearson, 'Groundwork of Eugenics', Eugenics Laboratory Lecture Series, 

 1909, p. 25. 



» Snow, Studies in National Deterioration, No. 7, p. 34. See also Beeton and 

 Pearson, 'Inheritance of the Duration of Life', Biometrika, vol. i, 1901, and 

 Elderton and Pearson, ' Further Evidence of Natural Selection in Man ', Biortietrika, 

 vol. X, 1915. 



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