Notions in Antiquity

             Aristotle: Male Form imposed on Female Substance: cf. sculptor on clay

                                                Left versus right testis (experimental?)

             Plato’s Symposium: Drinking party proposes origins as three pairs of conjoined twins

FF / MF / MM -> lesbian, hetero, gay

             Galen (ca 200 CE):  3 ♂ + 3 ♀ uterine locations determine sex of offspring

 

T Aquinas (~1250) contrasts male versus female anatomy

W Harvey (1578 – 1657): uterine scars in post-partum animals

A Vesalius /  L da Vinci: gross anatomy of anatomical differences

 

Modern Period

Eggs come from Ovary

                        R de Graaf (1641 – 1673): ovarian follicles

                                                                   Assumed follicle = ovum
                        KE von Baer (1792 – 1876): human ovum (1827)

Schwann: mammalian ovum as single cell (1834)

G Falloppio (1523 – 1262): oviduct conducts ovum -> uterus

T Bischoff (1807 - 1882): ovum in rabbit follicle (1842)

Sperm as agents of reproduction

A Leeuwenhoek (1688) sees human sperm: (non-reproductive) ‘animalcules’ ?

O Bütschli (1848 - 1920): mitosis in nematodes (1873)

E van Beneden (1846 - 1910): meiosis and pronuclei in Ascaris (2N = 4)
Fertilization
            L Spallanzani (1729 - 1799): artificial fertilization of frog egg w/ added sperm (1784)

                                                artificial insemination of dog (1780s)
            O Hertwig (1849 - 1922): pronuclear fusion of sperm & egg in sea urchins (1876)

            Cytology anticipates Mendelism

                        A Weismann (1834 - 1914): reduction division necessary in germ line theory (1880s)

                        H Henking (1858 – 1942): “X element” in male

                        C McClung (1870 – 1946): unpaired “X” in male grasshoppers only (1898)

                        T Montgomery (1873 – 1912): pairing of chromosomes in meiosis

                                W Sutton & T Boveri propose chromosomes follow Mendelian Laws (~1903)

                                      EB Wilson characterizes females w/ XX, males w/ XY: anticipates TH Morgan

                                   => First "Mendelian” trait: sex determination (though not “Mendelian”)

                        N Stevens (1861 – 1912): hetero-chromosome (later, Y) in Tenebrio (1905)

                                Alternatives

                                      XX & XO beetles (EB Wilson & students)

                                      L Doncaster (1877 – 1920): ZW & ZZ birds reverse mammalian pattern

                                      2N & N Hymenoptera ("queens" vs workers, drones): haplo-diploid sex determination

                                Dosage compensation (HJ Muller 1932)

                MF Lyon (1925 – 2014): heterochromatization (“Lyonization”) of alternate Xs

                Alternative (correct) explanation of tortoiseshell / calico cats

Hormonal mechanisms in sex determination

                F Lillie (1870 – 1947): origin of freemartin cattle (1916)

                                Fraternal twin ♂ /♀ cattle w/ anastomosed chorions: male “masculinizes” female

                                cf. 70% of women in Huxley’s “Brave New World” (1931)

                Testosterone isolated, synthesized (1934); restores virility to castrated birds, mammals

                                Follicle Stimulating Hormone (FSH) induces egg production

                                Luteinizing Hormone (LH) induces formation of corpus luteum

                                Anti-Mullerian Hormone (AMH) suppresses female structures

Non-standard combinations of cytology & hormonal environments

                “Hermaphrodites” (both genitalia)
                                vs “Pseudo-hermaphrodites” (contrasted internal & external genitalia)

                                Non-disjunction: XO (Turner Syndrome: 1938) XY XO mosaic Turner

                                Fusion: XX + XY at blastocyst stage “true” hermaphrodites

     SRY gene at Yp11.2

                                XY includes SRY [Sex-Regulating Y] locus  standard male

                                XY does not include SRY AIS (Androgen-Insensitivity Syndrome)
                                        Formerly known as TFS (Testicular Feminization Syndrome)

                                        External female genitalia & 2^o appearance: absent / streak gonads

                                XX with SRY insertion external male genitalia; sterile

                Contrast genetic, anatomy, & orientation sex & sexuality
                        In sport: the 1968 Olympics & subsequently

                                Learned vs Innate

                                      Genetic vs non-genetic innate

                                Evolutionary psychology

 

Implications of Sex

                Darwinian Sexual Selection

                            Secondary Sex characteristics (antlers, peacock tails, bright colors in (male) birds)
                            Deleterious as survival traits: e.g., more conspicuous to predators
                            Advantageous as reproductive trait: > Survival value

                Genetic Recombination
                            Asexual clones more successful in short-term, constant environment
                            Sexual species more successful in long-term, variable environments

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