Heredity, race, and society.

  • Leslie Clarence Dunn
Date:
1947
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Heredity, race, and society. Source: Wellcome Collection.

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    is us, and words of wisdom are of no avail without a brain to heed and retain them. On the other hand, inherited possibilities would never become actualities without the means by which they may grow and de velop. Nature and nurture are so obviously necessary and inseparable that the important question is not which is more important but rather how together they determine our qualities. Sexual Reproduction All our heredity, our nature, is transmitted to us from our parents through tiny cells which connect our living substance with that of our forebears. Each human being takes its origin from the union of two of these bits of living matter, an egg from the mother which has been fertilized by a single sperm from the father. The egg is a tiny sphere hardly visible to the naked eye; it has been estimated that twenty million human eggs would weigh about one ounce. A sperm is visible only with the aid of a microscope, and its volume is about eighty-five thousand times smaller than that of an egg. Furthermore, a sperm is quite different from an egg in appearance, being shaped like a thread inflated at one end to form a head. Some idea of the sizes of these living links between the generations has been given by an eminent American biologist, H. J. Muller, who has calculated that if we could collect together all the eggs from which the present human population of the earth has sprung—two billion two hundred millions of them—they would all occupy the volume of about two and a half quarts. The sperm cells—two billions of them —would occupy the space of half an aspirin tablet. We inherit our natures about equally from both parents, that is, father and mother are equally impor tant in the transmission of heredity. And yet, the male and the female sex cells are, as we have seen, extremely different in size and in appearance and structure as well. How can such different vehicles convey the same hered itary traits? Already in the nineteenth century some
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