The Bahama Islands furnish one of the stock examples. Clement A. Penrose writes7 of them:
"In some of the white colonies where black blood has been excluded, and where, owing to their isolated positions, frequent intermarriage has taken place, as for instance at Spanish Wells, and Hopetown, much degeneracy is present, manifested by many abnormalities of mind and body.... I am strongly of the opinion that the deplorable state of degeneracy which we observed at Hopetown has been in a great measure, if not entirely, brought about by too close intermarrying of the inhabitants."
To demonstrate his point, he took the pains to compile a family tree of the most degenerate strains at Hopetown. There are fifty-five marriages represented, and the chart is overlaid with twenty-three red lines, each of which is said to represent an intermarriage. This looks like a good deal of consanguineous mating; but to test the matter a little farther the fraternity at the bottom of the chart,—eight children, of whom five were idiots,—was traced. In the second generation it ran to another island, and when the data gave out, at the fourth generation, there was not a single case of consanguineous marriage involved.
Another fraternity was then picked out consisting of two men, both idiots and congenitally blind, and a woman who had married and given birth to ten normal children. In the fourth generation this pedigree, which was far from complete, went out of the islands; so far as the data showed there was not a single case of consanguineous marriage. There was one case where a name was repeated, but the author had failed to mark this as a case of intermarriage, if it really was such. It is difficult to share the conviction of Dr. Penrose, that the two pedigrees investigated, offer an example of the nefarious workings of intermarriage.