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Page:Popular Science Monthly Volume 61.djvu/40

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POPULAR SCIENCE MONTHLY.

among Cubans until full maturity, as a means of raising their physical standard. He found that at present the average Cuban man is, in size and weight, the equal of the American female student.

An illustration of environment, including education, overcoming hereditary tendencies has recently been brought to my notice by Mr. A. J. Redmon. Mr. Redmon reared two murderous sparrow-hawks in a cage with young larks and wrens. "They all grew up together; the little wrens would creep under the sparrow-hawks for protection at night. The two hawks never attempted to hurt the larks or wrens." Mr. Redmon tried to starve the hawks into killing birds, but they utterly refused to disgrace their education.

Galton has determined just how much, on an average, each ancestor contributes to the peculiarities of an individual. The parents together contribute one half of the total heritage, the four grandparents together one fourth, the eight great-grandparents one eighth, the sixteen great-great-grandparents one sixteenth and all the remainder of the ancestry one sixteenth.

PSM V61 D040 Generational physical contribution by an individual.pngFig. 1. Average Contribution to the Peculiarities, or deviation from the average, of the Individual, by the first, second, third, fourth and remaining generations; father and mother each contribute one fourth together one half of the total heritage. Each one of the grandparents contributes one sixteenth or together one fourth. The great-grandparents together one eighth, the great-great grandparents together one sixteenth, and all the remoter ancestry together one sixteenth. After Meston. This law explains another—that the offspring of exceptional parents are, on an average, less exceptional than their parents. Supposing that the average height of two parents exceeds the average height of the race by three inches. The average of the grandparents and remoter ancestors will differ from the average height of the race by much less than this. Since the ancestors beyond the parents contribute one half the entire heritage of the individual, they will act as a drag to pull the individual toward mediocrity, in the present case by one inch. This law acts impartially, so that the offspring of the extremely good and the extremely bad are both saved from the fate of their parents.

This regression toward mediocrity may readily be overcome by selective breeding. In race-horse breeding if the ancestry has been good for three or four generations the rest are not considered.

Galton has devised a forecast machine by which, if the height of the parents is known, the average height to which the offspring will grow