Full text: Problems in eugenics

42Section I.V. G. Ruggeri. 
noting the great importance which consanguinity has for the latter, not from 
the fact that the two parents are related but because they possess the same 
special recessive disposition, which tends to the appearance of the corre­ 
sponding anomaly, as can be verified also by so many tendencies of disease(i). 
Haecker(2), also, maintains that albinism, especially in the negro, is a 
recessive character, and cites the striking case of F arabee, not being 
acquainted with the case observed in Italy. 
More important for anthropology is normal pigmentation, dark or fair, 
brunette type or bilond type, as is commonly said. Former anthropologists 
have maintained that the blond type is simply a loss of colour from the 
brunette type, as if one were dealing with a garment or a coloured liquid, 
which loses its colour gradually with time. That view can no longer be 
maintained; from the new doctrine it is clear that it is not a question of a 
single character more or less attenuated, but that we are dealing with two 
characters clearly marked out from the time of the progenitors. 
It follows from the interesting researches of the Davenports that a total 
of 115 families, in which both the parents were fair, had 513 children, of 
whom only 1.75 per cent, were dark, which for various reasons is negligible, 
so that we may accept the rule that blond parents have only blond children. 
This is so because the blond mutation behaves similarly to the albino 
mutation : it is recessive in relation to the brunette type, hence the blonds 
are necessarily homozygote, that is to say pure types as regards pigmentation : 
their somatic and germ cells are entirely wanting in the brunette character. 
Quite a different behaviour must be expected, instead, for the brunette 
parents, who can be homozygote, but also heterozygote, that is to say may 
have the blond character latent in consequence of a previous crossing with 
the fair type. The possibility of such a crossing varies enormously with 
the country. With us, for example, the brunettes of Sardinia have the 
greatest probability of being pure types, that is to say homozygotesi, while 
such probability is least with the brunettes of the Venetian territory. But, 
apart from this criterion of probability, it is not possible to say a friori 
whether a brunette is homozygote or heterozygote. It may be demon­ 
strated, instead, from the descent that this type has been crossed with the 
blond type. Hence, if of four children two are blond and two brunette, it 
amounts to saying that the brunette parent was heterozygote, had the blond 
type latent, and thus is verified the aforesaid rale of 50 per cent. If, on 
the other hand, all the children are brunettes it amounts to saying that the 
brunette parent was homozygote, and therefore has wholly concealed its 
antagonist. If, finally, from two brunette parents there are four children 
one of whom is blond, it implies that both the parents were heterozygotes 
(1) J. Frédéric, Beiträge zur Frage des Albinismus. Zeitsch. f. Morph, u. Anthrop. X. 
(1897), p. 233-234. 
(2) V. Haecker, Op. cit. p. 245-246.

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