Heredity

1
Heredity
2
Examples of Domesticated Plants
3
Examples of Domesticated of Animals
4
Eternal Questions

• What is the nature of fertilization? What is
  transmitted during copulation that is responsible
  for conception?
• Can living things generate spontaneously, or is a
  sexual union always necessary for the production
  of new individuals?
• What are the respective contributions to the
  characteristics of a child made by the father and
  the mother? Does the mother make a genetic
  contribution in addition to serving as the nurse
  of the developing embryo?
• Where is the male semen formed in a special
  organ or throughout the body?
• How is the sex of the offspring determined?
• To what extend are the heritable characters
  affected by use or disuse, the environment, or
  other factors?

5
Ancient Greece and Roman eras (ca. 600 BCE-500
CE)

• Ancient Greek poetry (e.g., Homer's Iliad, 7th.
  Century BCE) shows a preoccupation by early
  Greeks on matters of pedigree and eugenic ideas
  were very popular

6

• Alcmaeon of Crotona (b. ca. 535 BCE) claimed that
  the semen originated in the brain, believed in
  the female semen and also postulated that the
  sex was determined by the preponderance of either
  one equal amounts would cause hermaphroditism

7

• Hippo of Rhegium postulated that semen was
  originated in the spinal cord
• He also said that children are either male or
  female according to whether the semen was thick
  and strong or weak and watery
• He believed that this could only be applied for
  the male semen, since the female one is
  discharged from the sexual organ

8

• Parmenides (515-440 BCE), Empedocles of Acragas
  (492-432 BCE), and Democritus of Abdera (late
  5th. century BCE) also believed in the female
  semen
• Parmenides thought that semen was derived from
  blood

9

• Empedocles held that the heat of the womb was
  decisive for sex determination a warm uterus
  produces males a cold one, females
• Censorinus (ca. 238 BCE) thought that it was the
  temperature of the semen, not the womb, the one
  that determined sex hotter male semen boy that
  resembles the mother if the mother is warmer
  girl that resembles her father equal degree of
  heat boy that resembles his father equal
  degree of coldness girl that resembles the
  mother

10

• In Parmenides, Anaxagoras (500-428 BCE), and in
  ancient Indian writings there is the Right and
  Left theory
• Boys come from the right and girls from the left
  side of the body (the same for the womb)
• This may be based on the old Greek belief that
  right was superior to left. This was combined
  with Empedocles heath theory and, thus, the right
  side of the womb was believed to be warmer

11

• They further believed that if sperm from the
  man's right side entered the right side of the
  uterus a boy would be born but if was all the
  opposite, then a female would be formed
• However, if semen from the right entered the left
  side, then a male with female features would be
  formed, and if semen with females characteristics
  entered the right side of the uterus, then a
  female with male features would be formed

12

• Anaxagoras further anticipated somewhat the
  Theory of preformation since he believed that a
  prototype of every part and every organ of the
  future living creature was already contained
  within the semen
• He thought that only males produce semen while
  females only play the role of conceiving

13

• Up to the 18th. century these beliefs were
  maintain up to point that many physicians even
  recommended that if a woman wanted to have a boy,
  she should lie on her right side
• Also, since it was believed that cold temperature
  made the womb to become hotter, it was
  recommended that if you wanted to have a boy,
  intercourse should take place in cold nights

14

• Diogenes of Apollonia (ca. 460 BCE) thought that
  blood was converted into semen when the thickest
  blood in the veins was absorbed by the fleshy
  parts of the body. The rest was transformed into
  a more liquid, warm, and foamy substance. Semen
  was carried out to the sex organs

15

• Hippocrates of Cos (ca. 460 - 370 BCE) based his
  ideas on observations and empirical approaches
  more than anything and systematized Greek medical
  knowledge
• He and Democritus foreshadowed Darwin's
  provisional hypothesis of panspermia or
  pangenesis (tiny particle called gemmules or
  pangenes are given off by every part of the adult
  body, a line of though derived from the school of
  atomism) in his work (De Genitura)
• He also believed in the inheritance of acquired
  characters

16

• Plato (427-347 BCE) asserted that the semen came
  from both, the brain and the spinal cord

17

• They believed in spontaneous generation (also
  called abiogenesis)
• Climate created different people
• Males were determined by strong sperm and
  females by weak one and also in the Right and
  Left theory
• This was evidenced by several statements

18

• When a woman is pregnant with twins, should
  either breast sag, she will lose one child (...)
  if it is the right breast, it is a male child
  that will be lost if it is the left breast, a
  female child since the male fetus is usually on
  the right, the female on the left (Aphorisms V,
  38)
• At puberty, depending on which testicle develops
  first, the individual will father boys if it is
  the right one, girls if it is the left
  (Epidemics V, 4, 21)
• The male fetus is in the warmest place, the
  most solid, at the right of the womb that is
  why males are darker and formed earlier they
  move about earlier then movement stops and they
  grow more slowly. They are more solid, more
  passionate, and more full-blooded because of the
  location in the womb where they take form is
  hotter (Epidemics VI, 2, 25)

19
Aristotle Distinguished Four Types of Generations

• Abiogenesis
• Bud formation (small animals being formed on the
  sides of larger ones, plants and crustaceans)
• Sexual reproduction without copulation (male and
  female attributes merged to such an extent that
  no copulations were needed hermaphroditism and
  parthenogenesis in plants, bees, fishes)
• Fertilization and copulation

20

• Aristotle speculated that the relative
  contributions of the female and male parents were
  very unequal the female was thought to supply
  what he called the matter and the male the
  mirion
• The male alone makes the seed from his blood it
  contains potentially the sensitive soul and the
  adult form, but actually it contains no bodily
  parts (an opposing view to those of preformism
  and pangenesis)

21

• For Aristotle the female contributes only the
  catamenia (menstrual blood) or material whose
  form is nutritive soul. When the male's form has
  been imposed upon the female material, the
  somatic part of the seed is a ploughed way all
  that is transmitted is soul, the source of form
  and motion
• If the fetus develops regularly, the father's
  form will be actualized failing that, the
  mother's failing that again, more distant
  ancestors successively, until eventually the form
  may be merely that of the species, or even just
  the genus Animal (that is, a monstrous birth)

22

• Aristotle criticized Hippocrates's ideas on the
  bases that sometimes an offspring resembled more
  way back ancestor than its own parents
• Also, how can an adult that later in life will
  become bold, transmits boldness before getting
  that characteristic? How to explain the
  inheritance of characteristics of dead tissues
  such as nails and hair? Or the inheritance of
  behavior? He was also against the idea of a
  miniature germ

23

• Aristotle thought that the Right and Left
  theory was wrong since he had found female
  embryos on the right side of the bomb (and male
  on the left)
• He did believe, though, that female perittoma
  (surplus of nutrient) lacked the vital heat
• He believed in hybridization to an extreme he
  thought that the giraffe was a hybrid between the
  camel and the leopard. He thought that the sperm
  derived from the blood. Menstrual blood was the
  substrate for the embryo and depending upon the
  reaction with it, certain characters would be
  more or less expressed

24

• Theophrastus of Eresus (ca. 371-287 BCE) studied
  under Aristotle and inherited his library
• He held that higher plants reproduced by sexual
  means, although this fact was ignored for many
  centuries. He described variation among plants
  and how they could be inherited (Historia
  plantarum, De causis plantarum)

25

• Herophilus of Chalcedon (last third of the 4th.
  century BCE) discovered the ovaries which he
  termed female testes
• He also described the uterus, the cervix and the
  Fallopian tubes and was interested in the
  relationship between menstruation and general
  health
• He thought that the spermatic duct was the
  principal organ of spermatogenesis

26

• Though the Romans did not contribute much to the
  theoretical foundations of reproduction and
  heredity, they did develop the study of applied
  genetics in selection, breeding, fruit grafting,
  etc.
• However, their time was marked with rampant
  superstition and mysticism as revealed in the
  writings of Pliny the Elder (23-79 CE)
• Stories about how women produced offspring
  related to their thoughts, species giving birth
  to totally different ones, incredible tales of
  hybrids, were very common among the authors of
  those times

27

• Athenaeus of Attalia dealt with hybrids in
  mythical ways. He introduced the concept of
  pneuma (spirit). He considered that this pneuma
  was responsible for the generation of semen
• Galen of Pergamum (129-ca. 199) still believed in
  the Right and Left Theory of sex determination
  (in De Semine) and the vital heat ideas
• The Institutes of Manu wrote in India between 100
  and 300 CE consider the role of the female like
  that of the field and of the male like that of a
  seed new bodies are formed by the united
  operation of the seed and the field

28
Medieval Times

• Writers like St. Augustin (354-440), St. Isidore
  of Seville (560-636), Vindician (632-712), and
  Michel Psellus (1018-1079) pretty much repeated
  much of the same old ideas of the ancients such
  as the Right and Left Theory
• The Arabs, although
  excellent horse
  breeders, just passed
  the Greek knowledge
  into future generations
• Such was the case of
  Avicenna (980-1037)

29
Albertus Magnus (1193-1280)

• Encyclopedist, Aristotelian
• Made contributions in Zoology and Botany
• Believed in spontaneous generation, the inherited
  of acquired characters, pangenesis, and the left
  and right theory

30

• He also distinguished four types of reproduction
  in sexual reproduction among the higher animals
  he taught that the material produced by the
  female was like a seed (a humor seminalis),
  differentiating it from the catamenia (menstruum)
  in mammals and the yolk of the egg in birds, but
  incorrectly identifying it with the white of the
  egg
• The cause of the differentiation of the sexes was
  that the male vital Heat could concoct semen
  out of surplus blood, whereas the female was too
  cold to effect the change

31
The Renaissance

• Leonardo da Vinci explained that blacks were not
  white people burned by the sun

32

• That black people in Europe have black
  descendants and that progeny between blacks and
  whites were gray supporting the contention that
  the mother also had some sort of sperm and
  potency regarding heredity

33
Paracelsus (Swiss, 1493-1541)

• He said that the semen contains an aura
  seminalis, some sort of semimaterial principle
  which was, in fact, responsible for heredity
• He also believed in panspermia and largely
  followed Hippocrates. The same can be said of
  writers such as Nicholas de la Roche and Martin
  Akakia (French, 1497-1551)

34
The Seventeenth Century

• William Harvey (ex ovo omni An egg is the
  common origin of all animals thus there is not
  spontaneous generation)

35

• Eggs had to be fertilized by the semen. He was
  the first to make a real contribution to the
  study of reproduction and heredity
• He presented two possibilities for the
  development of the egg after it had been
  fertilized by semen either the complete material
  was already present and merely needed to be
  shaped or the material had to be assembled and
  was differentiated as it was produced
• The former theory is known today as
  metamorphosis the second is epigenesis

36
Nehemiah Grew (English, 1641-1711)

• Suggested in 1672 that pollen represented the
  male element of flowering plants

37
Rudolf Jakob Camerarius (German, 1665-1721)

• Confirmed Grews ideas. In 1694 published De Sexu
  Plantarum Epistola in which he
• Designated the anthers as the male sex organs
• Pollen was needed for fertilization
• That sexual reproduction in plants
  was equivalent to that in animals
• The role played by wind in
  pollination
• Seeds may be produced under
  certain conditions even if
  pollination was prevented

38
Anton van Leeuwenhoek (Dutch, 1632-1723)

• Discovered the spermatozoa in 1677, but were
  these worms fertilizing agents of parasites as
  von Baer thought? Even if the former were true
  do you need all of the spermatozoans or just one
  for fertilization?

39

• Van Leeuwenhoek, his student Johan van Ham, and
  Nicolaas Hartsoeker (1656-1725) all assumed that
  the spermatozoon was a preformed organisms
• Martin Schurig (German, 1656-1733) in his 1720
  Spermatologia again suggests that the sperm is
  produced in the brain

40
The 18th. century, Preformation and Epigenesis

• The question was how can the amorphous egg
  developed into an adult? Two explanations were
  proposed The first one was called preformation
  that maintained that the embryo was preformed
  in the egg and that from there you got by growth
  the adult form
• An extreme view of this theory was the school
  that postulated the pre-existence of a
  miniaturized adult (homunculus) somehow
  encapsulated in the egg

41

• Preformationists were further divided on whether
  the preexisting embryo was located in the egg
  (ovists) or in the sperm (spermists)
• Marcello Malpighi (1628-1694), Albrecht von
  Haller (1708-1777), Charles Bonnet (1720-1793),
  and Lazzaro Spallanzani (1727-1799) were ovists
• Van Leeuwenhoek, Hermann Boerhaave (1668-1738),
  and Hartsoeker were spermists

42

• Spallanzani conducted between 1780 and 1785 the
  first experiments on artificial insemination
• He used male frogs dressed with little panties
  that allow the fluid to pass but not the
  spermatozoids and saw how they failed to
  fertilized the females. The experiments were
  abandoned after a uproar for trying to interfere
  in God's process

43
George Louis Leclerc, Compte de Buffon (French,
1707-1788)

• Published from 1739 on an encyclopedic Histoire
  Naturelle where he emphasized stories of animals
  over abstract classification
• Believed in pangenesis and that if more male
  particles were provided by the male, then it
  would be a boy and vice versa

44

• Similar ideas were expressed by René-Antoine
  Ferchault de Réaumur (1683-1757) and Pierre-Louis
  Moreau de Maupertuis (1698-1759)
• They were very critical of preformationism
  because the observation that offspring contain a
  mixture of characteristics of both parents, which
  was particularly true in the case of hybrids

45

• Maupertuis believed that the reason behind this
  explanation was the presence of particles in
  the semen and that excess particles were carried
  from one generation to another, which would
  explain that some people had more resemblance to
  their grandparents than to their parents
  themselves

46

• He discarded teleological explanations of
  biological adaptations. Believed in the survival
  of the fittest and in inheritance of acquired
  characters and in variation within species from
  which changes can evolve. He endorsed pangenesis
• The large number of spermatozoids would include
  cells from previous generations explaining, thus,
  the origin of resemblances to pasts generations

47
Epigenesis

• The gradual differentiation of the amorphous egg
  into the organs of the adult
• This idea was originated by Caspar Friedrich
  Wolff (1733-1794). In 1759 he published Theoria
  generationis and in 1764 Theorie von der
  Generation where he attack Bonnet's and von
  Haller's ideas

48

• Wolff proposed that the nourishment and growth of
  plants depends of an essential force, or vis
  essentialis, which has the power to assemble new
  organs not previously existent from bubbles
  (cells) of a homogeneous substance
• He believed in the cell as the unifying element
  of biology being, thus, a forerunner of the cell
  theory of Schwann's of 80 years later

49
Karl Ernst von Baer (German, 1792-1876)

• Published in 1828 a work describing animal
  development in different groups that showed
  progressive specialization throughout development
  while also showing irreconcilable differences
  among major groups
• He was the one who discovered the mammalian egg
  contained within the Graafian follicle of the
  ovary

50

• Both, Wolff and von Baer postulated that the
  mother supplied a single, more or less uniform,
  unit of matter (ovum) while the male supplied
  the potency (vis essentialis)
• This seemed to have been confirmed when Bonnet
  discovered in 1740 that egg of plant lice
  (aphids) can develop even without the presence of
  males
• That is what we call today parthenogenesis.
  Wolff was also extremely interested on the
  environmental factors affecting organisms in the
  short run (epigenetics)

51
Linnaeus

• He discovered the sexual nature of plants
• He defined species as similar individuals bound
  together by reproduction, in which eggs always
  produce offspring closely resembling parents.
  Hence, no new species are produced at the present
  time

52

• He was influenced by Rudolph Jacob Camerarius
  (1665-1721) and Vaillant. For plants he used
  differences in the number and position of the
  stamens and pistils of the flowers
• This sexual classifications was somewhat
  uncomfortable for Linnaeus and the society of the
  time because of moral reasons, but proved to be
  so useful that was widely adopted

53

• In 1841 Albrecht Kölliker (1817-1905) showed that
  spermatozoids were cells and R. Remak (1815-1856)
  in 1852 and Carl Gegenbaur (1826-1903) in 1861
  extended those ideas to the ovule
• In 1845 Johann Dzierzon (1811-1906) substantiate
  the hypothesis that drones come from unfertilized
  eggs of honeybees by uniparental reproduction
  (apomixis)
• Oskar Hertwing (1849-1922) demonstrated in 1875
  the conjugation of both nuclei after
  fertilization and all what was needed was a
  single spermatozoan

54
Insect Pollination

• It was discovered by Philip Miller (1694-1771) in
  1721
• In 1795 Christian Konrad Sprengel (1750-1816)
  published a classical treatise on the pollination
  of flowers by insects that emphasized that plants
  with flowers needed to be pollinated by animals
  and advanced elegant explanation of coevolution
• One must investigate the flowers in their
  natural environmentone must try to catch Nature
  in the act.

55
Plant Breeders of the 17th. and 18th. Centuries

• Cotton Mather's (1663-1728) described in 1716
  spontaneous crosses in maize and other plants
  demonstrating that pollen is essential for the
  formation of seed in maize
• Other hybridizers were Thomas Fairchild
  (1667-1729) and N. Guyot

56

• Josef Gottlieb Kölreuter (1733-1806) more
  complete (1761-1766) publications. He confirmed
  the significance of insects in pollination
• He was the first to undertake systematic
  hybridization experiments in plants. He carried
  out 500 hybridizations with 138 species of
  plants. No real hybrid was fertile. However,
  when he tried backcrosses, there was certain
  degree of fertility

57

• Kölreuter also found that F1 crosses were almost
  completely uniform and intermediate between the
  parents which would demonstrate blending
  inheritance
• He described correctly the characteristics of the
  F2 generation and varied between the two P forms.
  He also demonstrated that hybrids do not produce
  a third species (a statement general valid
  today). He established the significance of sex,
  fertilization and refuted preformation
• Félix d'Azara also observed (1801) animal hybrids

58
The Nineteenth Century

• Thomas Andrew Knight (1759-1838) worked with peas
  who described dominance and segregation (in back
  crosses) but did not count the different kinds of
  seeds and, thus, did not calculate the ratios

59

• The same happened with Giorgio Gallesio
  (1772-1839), who first employed the term
  dominant), John Goss (1822), Alexander Seton
  (1824), Thomas Laxton (1866, 1872), and Louis de
  Vilmorin (1816-1860) and his son Henry de
  Vilmorin (1843-1899) (reported in 1879)

60

• William Herbert (1778-1847) made a detailed
  analysis of the concept of species by examining
  whether the fertility of hybrids could be used as
  a criterion for membership in the same (or
  different) species
• He decided that the fact that hybrid offspring,
  whether fertile or sterile, are produced
  establishes that both individuals used in the
  cross have a common origin in the same genus and
  that there was no really sharp dividing line
  between varieties and species

61

• Hybridization work continued with A.F. Wiegmann
  (1771-1853), Augustin Sageret (1763-1851). They
  observed dominance, segregation, but never
  explained those phenomena, much less worked on
  ratios
• Carl Friederich von Gärtner (1772-1850)
  summarized in 1849 the results of nearly 10,000
  separate crossing experiments among 700 species
  yielding 250 hybrids. Observed regularities
  among hybrids but failed to enunciate any law

62
Charles Naudin (1815-1899)

• Published his accounts between 1855 and 1869. He
  studied a series of crosses involving several
  genera of plants

63

• He emphasized the identity of reciprocal hybrids,
  the relative uniformity of F1 as contrasted with
  the great variability of F2 he saw the
  recombination of parental differences in F2. But
  there was no analytical approach, no ratios were
  recognized (although they were obtained), and no
  simple and testable interpretations were tested
• The expression laws of Naudin-Mendel sometimes
  seen in the literature, is wholly unjustified.
  The same can be said of D.A. Godron (1807-1880)
  and M. Wichura (1865)

64

• These and other plant breeders such as Augustin
  Sageret (1763-1851) failed to think in population
  terms and to ask questions about the underlying
  mechanisms
• That would not take place until Mendel.