Recognized HTML document
Previous Index Next

18   Life and Letters of Francis Galton

determine it quantitatively. Actually for his data we have the following correlations

Father   Mother

Son   -396+-024   -302+-027

Daughter   -360+-026   -284+-028

There was thus really quite a well-marked prepotency of the father in the case of stature. Later results on ampler and better material have failed to confirm this prepotency t ; I think it may well have been due to amateur measuring of stature in women, when high heels and superincumbent chignons were in vogue; it will be noted that the intensity of heredity decreases as more female measurements are introduced. Daughters would be more ready to take off their boots and lower their hair knots, than grave Victorian matrons. As we have not since succeeded in demonstrating any sex prepotency in parentage, Galton's assumption that such did not exist justifies his theory. But this assumption was not justified by his actual data and affects seriously the values of the constants he reached, which are all too low in the light of more recent research. I think we should be inclined to say now that the regression of the' offspring deviate $ is on the average nearer to 5 than to Galton's 3 of the midparental deviate. Galton, however, recognised very fully that his numerical values were only first approximations. He writes

"With respect to my numerical estimates, I wish emphatically to say that I offer them only as being serviceably approximate, though they are mutually consistent, and with the desire that they may be reinvestigated by the help of more abundant and much more accurate measurements than those I have at command. There are many simple and interesting relations to which I am still unable to assign numerical values for lack of adequate material, such as that to which I referred some time back, of the relative influence of the father and the mother on the stature of their sons and daughters.

"I do not now pursue the numerous branches that spring from the data I have given, as from a root. I do not speak of the continued domination of one type over others, nor of the persistency of unimportant characteristics, nor of the inheritance of disease, which is complicated in many cases by the requisite concurrence of two separate heritages, the one of a susceptible constitution, the other of the genus of the disease. Still less do I enter upon the subject of fraternal deviation and collateral descent§."

Galton's reasons for making a special study of stature are dealt with at considerable length and summarised as follows:

"The advantages of stature as a subject in which the simple laws of heredity may be studied will now be understood. It is a nearly constant value that is frequently measured and recorded, and its discussion is little entangled with consideration of nurture, of the survival of the fittest, or of marriage selection. We have only to consider the midparentage and not to

* Phil. Trains. Vol. 187 A, p. 270, 1896.

t See Biometrika, Vol. ii, p. 378, 1902.

1 Galton in this paper introduces the term "deviate": "I shall call any particular deviation a ' deviate,"' Journ. Anthrop. Instit. Vol. xv, p. 252. The term was perhaps unnecessary considering the existence of " deviation," but it has come into general use, and is perhaps more justifiable in Galton's sense than "variate," which is now so often used, not for a particular variation, but for the " variable " itself.

§ Journ. Anthrop. Instit. Vol. xv, p. 258.

Previous Index Next