Page:Popular Science Monthly Volume 81.djvu/370

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364
THE POPULAR SCIENCE MONTHLY

THE INHERITANCE OF FECUNDITY[1]
By Dr. RAYMOND PEARL

MAINE AGRICULTURAL EXPERIMENT STATION

A THOROUGH and searching investigation of two great biological problems is a necessary prerequisite to any substantial advance of the science of eugenics. These problems are:

1. The mode of inheritance of human characters and traits of all kinds.

2. The physiology of reproduction in man, particularly with reference to human fecundity and fertility.

The progressive decline of the birth-rate in all, or nearly all, civilized countries is an obvious and impressive fact. Equally obvious and much more disturbing is the fact that this decline is differential. Generally it is true that those racial stocks which by common agreement are of high, if not the highest value, to the state or nation, are precisely the ones where the decline in reproduction rate has been most marked.

The causes concerned in the production of these results are without question exceedingly complex and difficult, if not impossible, of complete analysis. But of one thing we may be certain; somewhere in the complex of causes is included the biological factor as one element. Fecundity and fertility are physiological characters of the organism, subject to variation and capable of being inherited, just in the same manner as structural characters. We must be in possession of definite information regarding the physiology of fecundity and fertility, before it will be possible to make safe and sure advance in the social and eugenic analysis of matters involving these factors, such as, for example, the declining birth-rate.

The basic eugenic significance of that characteristic of organisms termed fecundity furnishes sufficient justification, I hope, for bringing to the attention of this Congress certain results regarding fecundity in one of the lower animals, namely the domestic fowl. In some particulars the results are, I believe, novel. They indicate, for the first time, the precise mode by which this complex physiological character fecundity is inherited. It will be the purpose of this paper to present—necessarily very briefly and without the detailed supporting evidence—the essential results of a study of fecundity in poultry, pointing out at the end some possible eugenic bearings of the results:[2]

  1. This paper was read at the First International Eugenics Congress, held in London, July 24-30, 1912.
  2. The results set forth below were first presented at the meeting of the American Society of Naturalists at Princeton, N. J., in December, 1911. A