History of GeneticsWhy study the history of genetics?Prehistoric geneticsEarly historical periodEarly scientific background: The four Lsvan Leeuwenhoek (1632 – 1723)Linnaeus (1707 – 1778)Lamark (1744 – 1829)Lyell (1797 – 1875)Modern genetics: Fertilization and gestationCharles Darwin (1809 -1882) and his HeritageGregor Mendel (1822 – 1884)Early cell biologyBirth of genetics as a unified fieldReferencesChapter 1History of Genetics1.1 Why study the history of genetics?George Santayana gave us the most powerful reason for studying the historyof anything: “Those who cannot remember the past are condemned to repeatit “ (Santayana, 1906). This topic deals with the developmental backgroundto the science of genetics as it emerged in the early part of the 20th century.The subsequent chapter, Genes, Politics, and Society outlines the unhappy anddisastrous social consequences of extrapolating “scientific genetic principles” intopublic policy before the science is well understood.1.2 Prehistoric geneticsWe have good empirical evidence that humans had an implicit knowledge of ge-netics from at least 15,000 years BCE. Surprisingly as it may sound, the evidenceresides in the remnants of the first attempts at genetic engineering. This engi-neering took the form of what today is called artificial selection—the deliberatebreeding of plants and animals for de sired characteristics. The best empiricalevidence comes from the analysis of pollen in hermetically sealed ancient tombsand from the dog.Current phylogenetic1analyses suggest that dogs evolved from wolves andwere domesticated at least by 15,000 BCE in Asia (Ostrander et al., 2008;Savolainen et al., 2002). The “at least” part of this temporal estimate derivesfrom archeological and DNA evidence of North American dogs suggesting thatthey were brought into the continent from Asia by the new world’s originaldiscoverers. Artificial selection of the dog for behavioral traits like herding,guarding, hunting, and retrieving is some of the best evidence for genetic influ-ences on mammalian behavior (Scott and Fuller, 1965).1Phylogenetics explores the genetic origins of species and the genetic relationships amongspecies.11.3. EARLY HISTORICAL PERIODCHAPTER 1. HISTORY OF GENETICSLike many attempts to manipulate nature, early genetic engineering h adunforeseen consequences. Merell (1975) reported that the original progenitorsfor today’s onions, lentils, ginger, and many other crops are extinct, probablybecause our human ancestors selected for fecundity. So called “wild onions” and“wild ginger” are really domestic varieties that “got loose” and outcompetedtheir wild type ancestors.1.3 Early historical periodHaving an implicit knowledge is very different from the explicit knowledge re-quired of a science. You know how to tie your shoelaces. Think for a minuteabout writing a professional article on how to tie a shoelace. The former isimplicit knowledge. The latter is the explicit, scientific knowledge.According to Stent (1971), the first known theory of inheritance in Westernthought originated in Greece in the fifth century BCE and was taught (andprobably developed) by Hippocrates. One could classify Hippocrates ideas as a“bricks and mortar” theory. That is, th e hereditary material consists of physicalmaterial (as opposed to a blueprint). He postulated that elements from all partsof th e body became concentrated in male semen and then formed into a humanin the womb. He also believed in th e inheritance of acquired characteristic.The large biceps of an Olympic weight lifter result in many “bicep parts” in thesemen. Hence, his children would also have big biceps.Agenerationlater,Aristotlecriticizedthistheory. Hisfirstobjectionwasthat mutilated and physically handicapped people can have normal children. IfKostas had lost his left arm in battle, then he has no “left arm parts.” Howcome his children have perfectly formed left arms?Aristotle’s second objection was more subtle—people can transmit charac-teristics that they do not show at conception but develop at a later age. Thinkof gray hair or male pattern baldness. At th e time of conception, most Greeksof the period would have brown to black hair and only a few would exhibit pat-tern baldness. Hence, there are no “gray hair parts” and few “baldness parts”although much later in life those “body parts” might be available. S till parentscan transmit these traits to their offspring.Aristotle went on to reject the bricks and mortar model of hered ity trans-mission. Instead, he proposed that heredity involved the transmission of in-formation—a “blueprint model.” This remarkable insight was ignored until themiddle of the 20th century. All subsequent theories were based on the bricksand mortar model.1.4 Early scientific background: The four LsGenetics did not developed suddenly. Sure, there were very important contri-butions that radically changed the field. Think of Darwin or Mendel. But evenDarwin’s paradigm shift did not occur de novo. Instead, it evolved from the2CHAPTER 1. HISTORY OF GENETICS1.4. EARLY SCIENTIFIC BACKGROUND: THE FOUR LSintellectual background of his time. Indeed, his grandfather, Erasmus Darwin,had written—albeit vaguely—about evolution. Here, we focus on “the four Ls”or four people whose surnames begin with the letter L that contributed to theintellectual climate that presaged genetics.1.4.1 van Leeuwenhoek (1632 – 1723)The first L is Anton van Leeuwenhoek. Many texts mistakenly credit vanLeeuwenhoek with the invention of the microscope. Actually, that instrumentwas first developed around 1590, some 40 years before van Leeuwenhoek’s birth,by two of his Dutch compatriots, the father and son team of spectacle makers,Zaccharis and Hans Janssen. Galileo further d eveloped Janssens’ invention intothe telescope.The major contributions of van Leeuwenhoek were his significant improve-ments to the microscope that enabled him to observe what he termed animal-cules,todaycalledmicrobesormicroorganisms. ManyconsidervanLeeuwen-hoek the father of microbiology. Even if one were to dispute this, there is nodoubt that he was the first to rep ort on single cell organisms. Scientists of theday greeted his finding with suspicion and resistance. It was not until a teamof impartial observers replicated van Leeuwenhoek’s observations that microbeswere accepted as a real phenomenon.Hence, his major contribution was to initiate