Historical Hypotheses of Inheritance

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Historical Hypotheses of Inheritance
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• For much of human history people were unaware of
  the scientific details of how babies were
  conceived and how heredity worked.

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• Clearly they were conceived, and clearly there
  was some hereditary connection between parents
  and children, but the mechanisms were not readily
  apparent.

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• The Greek philosophers had a variety of ideas.

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• Hippocrates speculated that "seeds" were produced
  by various body parts and transmitted to
  offspring at the time of conception.

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• Aristotle thought that male and female semen
  mixed at conception.

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• Aeschylus proposed the male as the parent, with
  the female as a "nurse for the young life sown
  within her".

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• With the invention of the microscope in the
  1700s, some scientists speculated they saw a
  "little man" (homunculus) inside each sperm.

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• These scientists formed a school of thought known
  as the "spermists".

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• They contended the only contributions of the
  female to the next generation were the womb in
  which the homunculus grew, and prenatal
  influences of the womb.

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• An opposing school of thought, the ovists,
  believed that the future human was in the egg,
  and that sperm merely stimulated the growth of
  the egg.

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• Another idea, pangenesis, was an idea that males
  and females formed "pangenes" in every organ.

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• These pangenes subsequently moved through their
  blood to the genitals and then to the children.

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• The terms "blood relative", "full-blooded", and
  "royal blood" are relics of pangenesis.

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• Francis Galton experimentally tested and
  disproved pangenesis during the 1870s.

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• Gregor Mendels work in the new field of genetics
  during the 1840s provided insight on the topic of
  heredity.

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• We are going to begin our exploration of genetic
  by learning about what this important scientist
  discovered.