Full text: Problems in eugenics

R. C. Punnett. Biology and Eugenics.i5 
By R. C. Punnett, 
Professor of Biology, Cambridge. 
To the student of genetics, man, like any other animal, is material for 
working out the manner in which characters, whether physical or mental, 
are transmitted from one generation to the next. Viewed in this way he 
must be regarded as unpromising, not only from the small size of his 
families, the time consumed in their production, and the long period of 
immaturity, but also because full experimental control is here out of the 
question. For these reasons man is of interest to the student of genetics, 
chiefly in so far as he presents problems in heredity which are rarely to 
be found in other species, and can only be studied at present in man him­ 
self. The aim of the Eugenist, on the other hand, is to control human 
mating in order to obtain the largest proportion of individuals he con­ 
siders best fitted to the form of society which he affects. It is 
evident that to do this effectually he must have precise knowledge of the 
manner in which transmission of characters occurs, and more especially of 
those with which he particularly wishes to deal. Precise knowledge is at 
present available in man for relatively few characters; and those characters, 
such as eye-colour, and certain somewhat rare deformities, are not the 
kind on which the Eugenist lays great stress. The one instance of eugenic 
importance that could be brought under immediate control is that of feeble­ 
mindedness. Speaking generally, the available evidence suggests that it is a 
case of simple Mendelian inheritance. Occasional exceptions occur, but 
there is every reason to expect that a policy of strict segregation would 
rapidly bring about the elimination of this character. 
There is reason to suppose that many human qualities are more compli­ 
cated in their transmission, and it is probable that certain phenomena now 
being studied in plants and animals will throw definite light upon man. 
Though characters are frequently transmitted on the Mendelian scheme quite 
independently of one another, there are cases known in which they are linked 
up more or less completely in the germ cells with the determinant of a par­ 
ticular sex. Sex-limited inheritance of this nature has been carefully worked 
out in particular cases in Lepidoptera and poultry. As yet there is much 
to be learnt in this direction, and further progress may be expected to lead 
eventually to a precise knowledge of the mode of transmission of many 
human defects, such as colour-blindness and haemophilia. It is not un­ 
likely that a similar mode of transmission will be found to hold good for 
many human characters usually classed as normal.

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