In the year of 2000, President Bill Clinton stood before the nation and made an announcement that was 47 years in the making; the preliminary draft of the Human Genome Project was complete. Indeed, we have come a long way since the influential discovery made by James Watson and Sir Francis Crick, but even their wildest imaginations could not comprehend the effects of the insight that they shared with the scientific world that day.
Curiosity of how "like begets like" can be traced back as far as the ancient Greeks. Hippocrates, among many other philosophers, pondered heredity and came up with the theory of pangenesis, which states that sex involves the transfer of miniaturized, invisible body parts (Human Genetics, Notes p. 407). Preformation was another popular idea early in the history of humans. Preformationism contended that either the egg or the sperm contained a miniature person called a homunculus; development was a matter of growing once outside the womb (DNA Watson). Genetic disease under the premise of preformationism was interpreted in various ways: the wrath of God, the mischief of demons, deficits in the "seed", or wicked thoughts by the mother (DNA Watson). Napoleon so feared the last of these interpretations that he passed a law that permitted poor, expecting mothers to shoplift (DNA Watson)! .
This biggest advance in genetics at the time came when Charles Darwin, in support of his theory of evolution by natural selection, put forth a modified version of pangenesis (DNA Watson). According to Darwin, the organs of an animal had "gemmules" that accumulated in the sex organs and were consequently exchanged during sexual reproduction (Darwin Species). His theory differed from the original pangenesis line of thought in that gemmules were in constant production during the organism's lifetime, thus if an advantageous change were to affect the organism, it could be passed on to its offspring (Darwin Species).