On the phenomena of hybridity in the genus homo / by Paul Broca ... ; edited with the permission of the author, by C. Carter Blake.

  • Paul Broca
Date:
1864
Catalogue details

Licence: Public Domain Mark

Credit: On the phenomena of hybridity in the genus homo / by Paul Broca ... ; edited with the permission of the author, by C. Carter Blake. Source: Wellcome Collection.

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    26 INTERMIXTURE OP CERTAIN RACES tion of the speciesj and provided it can repair the loss at every generation, the crossing- would still be eugenesic, nor would it cease being so^ even if the breed were only half as strong as their parents, and only half as long-lived. When, therefore, a physiologist wishes to demonstrate the existence of that degree of hybridity which we have termed eugenesic, he selects two perfectly recognised distinct species of animals, crosses them, studies their breeds, and if he finds that they are indefinitely proHfic, it is sufficient for him to affirm the existence of engenesic hybridity—that is to say, that the physiological definition of the species is unacceptable. But when a zoologist, in studying two races of animals, the specific determination of which is still contested, endeavours to estab¬ lish that these two races are merely varieties of the same species, and when in order to weaken the differential anatomi¬ cal characters pointed out by his adversaries, he invokes the physiological analogy exhibited by intermixture, we have a right to expect more than a partial demonstration. We must first prove that the intermixture of the two races constitutes a case of eugenesic hybridity ; for if the cross-breed are not be¬ tween themselves indefinitely prolific, it is certain that the two races are not of the same species. This first point being es¬ tablished, would not yet lead to any conclusion, since animals of difierent species may engender eugenesic breeds. He must, therefore, completely analyse all the phenomena of reproduc¬ tion and prove that they are exactly the same in the parent races and in the hybrid race. It is not merely the sexual ana- logy but the sexual identity which must be rendered evident ; for from his point of view, it is not sufficient that the tлvo races in question should be homogenesic in some degree, they must be entirely homogeneous, and the least genital difference be¬ comes an argument against the proposition he sustains. If the cross-breed, though very prolific, are less so than their parents, or less productive in their crossings than their direct alliances; or, finally, if the investigation of these crossings exhibits any functional inequality, it might become very probable that the tлvo races do not belong to the same species. Such would also be the case if the cross-breed were less strong and vivacious
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