Transcript Science Is “Doing One`s Damndest with No Holds Barred

“ ‘Doing One’s Damndest with No
Hold Barred’: Pluralism in
Methodology in History and
Philosophy of Science”
Springer Lecture
International History and Philosophy of
Science Teaching Conference
Calgary
June 25, 2007
Outline
I.
Introduction: The Importance of History and
Philosophy in Teaching Scientific Methodology
A.
“Should History of Science Be Rated X?”
B.
History and Philosophy of Science are
complementary but they are not the same
II. Logic of Science: What It Can Teach
III. The Case History Method
A.
Development of the Mendelian-Chromosome
Theory of Heredity (MCTH)
B.
Methodological Points
C.
Extensions to Social/Political Context
Outline
I.
Introduction: The Importance of History and
Philosophy in Teaching Scientific Methodology
A.
“Should History of Science Be Rated X?”
B.
History and Philosophy of Science are
complementary but they are not the same
II. Logic of Science: What It Can Teach
III. The Case History Method
A.
Development of the Mendelian-Chromosome
Theory of Heredity (MCTH)
B.
Methodological Points
C.
Extensions to Social/Political Context
Background
(Addison-Wesley, 1982)
(Wiley, 2001)
Should the History of Science be
Rated “X”?
[Stephen Brush: Science 183 (1974):1164-1172]
• Should students be exposed to the real history of
science?
- Brush’s answer was to assert that the “real”
history of science would clearly undermine the
textbook picture of scientific process
- Whig history and the cult of “objectivity”
- We know so much better now than our
predecessors
• Brush ends up supporting use of accurate history
Major Points in Today’s Talk
• History and philosophy of science can be useful in
teaching both the concepts and methods of science
• A historical and philosophical approach can
humanize science as a more every-day sort activity which can empower students
• An important component of science is its socioeconomic context: cultural factors that play a part in
how concepts are formulated and understood
• Accurate use of case histories can provide one of the
best ways to introduce “methods” in science
Outline
I.
Introduction: The Importance of History and
Philosophy in Teaching Scientific Methodology
A.
“Should History of Science Be Rated X?”
B.
History and Philosophy of Science are
complementary but they are not the same
II. Logic of Science: What It Can Teach
III. The Case Study Method
A.
Development of the Mendelian-Chromosome
Theory of Heredity (MCTH)
B.
Methodological Points
C.
Extensions to Social/Political Context
Logic of Science
• Components:
- Observation(s)
- Fact(s)
- Conceptualizations
• Processes
- Induction
- Deduction (If . . . Then reasoning, hypothesis
testing)
Outline
I.
Introduction: The Importance of History and
Philosophy in Teaching Scientific Methodology
A.
“Should History of Science Be Rated X?”
B.
History and Philosophy of Science are
complementary but they are not the same
II. Logic of Science: What It Can Teach
III. The Case History Method
A.
Development of the Mendelian-Chromosome
Theory of Heredity (MCTH)
B. Methodological Points
C. Extensions to Social/Political Context
Case History Method
DEVELOPMENT OF THE
MENDELIAN CHROMOSOME
THEORY OF HEREDITY (MCTH)
• Time Frame: 1866-1920
• Core Idea: Units of heredity are located in a linear
array on structures known as chromosomes in the
cell nucleus
• Involved the joining of two independent lines of
investigation:
The Mendelian-Chromosome Theory Is
An Interfield Theory
Mendelian-Chromosome
Theory of Heredity (MCTH)
Mendelian Plant
Hybridization Exps
Cytological Study of
Chromosomes
Standard Story
• Mendel’s work, published in 1866, was ignored
for 35 years, rediscovered in 1900 and rapidly
accepted thereafter
• In 1910 T.H. Morgan (Columbia Univ), looking
for Mendelian variations, found a white-eyed male
Drosophila, & established the idea of sex-linkage
• The linkage concept was extended to all the
chromosomes by Morgan and his group, who then
developed the method of chromosome mapping
• The new science of “genetics” developed largely
as an academic effort with little or no connection
to agricultural or commercial interests
Almost All Aspects of this History
are Misleading
• It makes the development of ideas seem too
logical and neat
• Ignores controversies and biases that were an
important part of the story
• Provides no historical/social/economic context
• It obscures some of the real logic and creativity in
science, the unclear path and fumbling steps as
biologists at the time were experiencing their work
• Supports the “treasure-hunt” concept of
knowledge-building
Core Mendelian Concepts
• Traits (characters) in organisms are represented by two
“factors” each passed down from the organism’s parents
• Traits can have two (or more) forms (tall, short)
• Dominance and recessiveness (symbolized T, t; Y,y)
• Members of each pair of factors separate from each other
(segregate) in forming germ cells (gametes)
• When considering 2 or more traits, maternally-derived
factors and paternally-derived factors assort
independently of one another:
TtYy yields TY, Ty, tY, and ty gametes
• Hybrids do not breed true
Rediscovery and Early Promotion
• Mendel’s work was
rediscovered independently by
three investigators in 1900
(Carl Correns, Hugo De Vries
and Erich von TschermakSeysenegg)
• Initial promotion carried out
particularly by William
Bateson in England and U.S.
• Mendel’s ideas provided what
appeared to be the first
comprehensive concept of
heredity
Reception of Mendel’s Work
• Highly favorable reaction in agricultural circles
- Provided a method for the analysis of hybrids
- Mendel’s approach was highly empirical,
experimental, quantitative and predictive
- It thus fit perfectly the demands of industrial
agriculture at the time for predictability and
control
• Many academic biologists (including the English
biometricians) were far more skeptical
Opposition to Mendelism
• One of those biologists who
was critical of Mendelism was
T.H. Morgan (1866-1945) at
Columbia University.
• Morgan’s background
- B.A. State University of
Kentucky, 1886
- Ph.D. Johns Hopkins, 1891
- Wrote his thesis on the
morphology and phylogeny of
the “Pycnogonids” (sea spiders)
Morgan and his son at Woods Hole, 1907
Morgan’s Morphological Work
• Aim was to determine
the evolutionary
relationships of the
Pycnogonids to other
invertebrates: Arachnids
or Crustaceans
• Morgan found the early
embryology supported
an Arachnid ancestry
• He soon abandoned
morphology as too
speculative, inconclusive
From Morphology to Experimental
Embryology, 1891-1900
• Disenchanted with
morphology,
Morgan was
inspired by the
experimental
embryology of Hans
Driesch at the
Naples Zoological
Station (1891, 1895)
• Experimentation
became a symbol of
the “new biology”
The Stazione Zoologica in 1874
Morgan’s Opposition to Mendelism,
1903-1909
1. Did not seem universal
2. Dominance and recessiveness are not usually as clear
cut categories as “tall” and “short” in peas
3. Mendel’s system could not explain inheritance of sex
4. Mendelian”factors” (not yet called “genes”) were
hypothetical units
5. To explain complex cases Mendelians invented new
“factors” arbitrarily:
“In the modern interpretation of Mendelism,
facts are being transformed into factors at a rapid
rate. If one factor will not explain the facts, then
two are invoked; if two prove insufficient, three
will sometimes work out. The superior jugglery
sometimes necessary to account for the results
are often so excellently explained because the
explanation was invented to explain them, and
then presto! Explain the facts by the very factors
that we invented to account for them.”
[Morgan, “What are factors in Mendelian inheritance?” American Breeders’ Association
Report 5 (1909): p. 365]
6. Mendel’s “Factors” sound like the old
embryological theory of preformation
• Preformation was a 17th early 19th century view that
the embryo was fully
formed within the egg or
sperm
• By 1830 it had been rejected
by most embryologists
• Preformation ignored the
qualitative process by which
new form arises from
undifferentiated matter
QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture.
Hartsoeker, 1694
Development of the Chromosome Theory
• By 1900 it had become
clear that chromosomes:
- Had something to do
with heredity either
directly or indirectly
- Existed in pairs in the
cell nucleus
- Each pair was
qualitatively different
(“individuality of the
chromosomes”) from
the others
Between 1890 and 1910 Two Lines of
Work Implicated Chromosomes In . . .
• The determination of sex
• Mendelian heredity, as possibly equivalent
to Mendel’s “factors”
• Both areas were a matter of considerable
controversy
Two Contrasting Theories of Sex
Determination, 1890-1910
• External Factors: Factors external to the sperm
and egg, acting on the fertilized or unfertilized
egg, determine sex
• Internal Factors (to sperm or egg): Some
intrinsic factor within the gametes (one or both)
determines sex at the time of fertilization
Much Attention Directed at the “Accessory
Chromosome” As Sex Determiner
• In many organisms one
pair of chromosomes consists of two different-sized
members, or of only a
single member; the lone
chromosome or its smaller
partner were called the
Accessory Chromosome
• Was it a sex-determining
chromosome?
The Chromosomal View Gained
Considerable Support by 1905
Edmund Beecher Wilson (1856-1938
Nettie M. Stevens (1861-1912)
1905-08 Wilson and Stevens Formulated
A Chromosome Theory of Sex
Determination
• In most animals:
XY or XO = male, XX =
female
• In birds and Lepidoptera:
XY = female, XX = male
• By early May, 1905, Stevens
had come to a firm conclusion
that the XY (XO) relationship
determined sex. Wilson was less
sure, until he read a draft of
Stevens’ paper in late May. He
published his results in October,
Stevens in November
Accessory chromosomes
Unification of the Chromosome and
Mendelian Theories
As early as 1902 Walter S. Sutton, a student of E.B.
Wilson, was studying meiosis in the grasshopper;
he suggested that:
• The movement of chromosomes during formation
of germ cells parallels Mendelian segregation
• The distribution of maternal and paternal members
of each pair to the poles appeared to be random,
leading to a large number of possible combinations:
2N = 10: 1,024
2N = 20:1,048,576
• By 1905 Wilson and others supported the parallel
Morgan Opposed the Chromosome Theory,
Especially in Relation to Sex
• Chromosomes dissolve after mitosis/meiosis and
thus may not maintain any structural integrity
• Differing patterns of male and female
chromosome complements:
XY, XO = male, XX = female (mammals, insects)
XX = male, XY = female (birds, butterflies)
• Preformation argument: Postulating chromosomes
as causal agents doesn’t explain anything: they are
simply structures
Morgan Also Opposed Natural Selection as
the Main Mechanism of Evolution:
• Selection of small individual variations, on which
Darwin relied, could never create a new species
• Small individual variations were often trivial and
non-adaptive
• Small variations, even if adaptive, would be
swamped out by interbreeding with the more
common form
• As an alternative, Morgan supported Hugo De
Vries’ “Mutation Theory”, 1901-1903: New
species arise in one step (“Mutation”) from their
parents
1907-1909: Morgan and His Students
Had Been Raising Fruit Flies to Test,
Alternatives to Darwinian Theory
• Neo-Lamarckism:
- Student had raised the fruit fly, Drosophila for
60+ generations in the dark, to see effects on eyes
- Results were completely negative
• Hugo De Vries’ “Mutation Theory”:
- In order to try to create De Vriesian mutations,
Morgan radiated flies, altered diet, temperature
- Results were negative
Drosophila, However, Did Turn Out To
Be A Favorable Laboratory Organism
• Produces new generation in 12-15 days
• Easy to keep in laboratory
• Produces large number of offspring each generation
By 1909, Morgan Ha Become
Discouraged with Drosophila Work
• In December he told his Yale colleague Ross
Harrison: “I have wasted two years [on these flies]
and gotten nothing from it.”
• Starting in January, 1910, he noticed some small
but discrete variations (which he called
“mutations”): Trident, Olive, Speck
• They were not species-level differences, however
• They all showed some characteristics of
Mendelian inheritance, but were not clear-cut
Morgan’s “Trident” Mutation
Then, By Chance, in May, 1910, Morgan
Found Another Mutation:
• Drosophila normally
have brick-red eyes 
• One day he observed a
white-eyed male fly in
his cultures
• The eye-color was a
clearly discontinuous
variation and proved to
be easier to work with
Morgan Bred the White-eyed Fly
to Red-eyed (Wild-type) Female
White Male
Red Female
X
All Red Offspring
F1
Red F1 Male
X
Red F1 Female
F2 Red Females White Females Red Males
2,459
0
1,011
The red/white-eye ratio was 3:1, but . . .
All the white-eyed flies were male!
White Males
782
Morgan’s Initial Explanation
• The 3 : 1 ratio, and the dominance of red over
white suggested a Mendelian pattern
• But how explain that only males showed the
recessive condition?
• Morgan symbolized the mating as follows:
Parental generation:
Red Female = RRXX x White Male = WWX_
F1 Generation:
Females = RWXX (red) Males RWX (red)
50%
50%
Morgan’s Cross Could Be Written
as Follows:
P1
Gametes
F1
Gametes
F2
Red Female
RRXX
WX
RWXX
Red Females
WX
RX
RRXX
Red Female
x
White Male
WWX
WX X
RWX
Red Males
RX
W
x
RWXX
Red Female
RWX
Red Male
WWX
White Male
There was one problem: Would have to assume the R
factor always segregated with the X factor in F1 males &
these males would produce no WX gametes
Testing Hypotheses
• Morgan proceeded to provide a set of tests, for example,
in the make-up of the F2 females:
“. . . There should be two classes of females in the F2
generation, namely RRXX and RWXX. This can be tested
by pairing individual females with white males (WWX).
In the one instance (RRXX) all the offspring should be
red — RWXX and RWX — and in the other instance
(RWXX) there should be four classes of individuals in
equal number, thus: RWXX, WWXX, RWX, [and]
WWX. Tests of the F2 red females show in fact that these
two classes exist.”
[Morgan, Science 32 (1910): 121]
The Test in Morgan’s Notation:
ParentF1
Female
(Red-eyed)
RWXX
F2 Red Females
129
RWXX
x
White Male
(White-eyed)
WWX
White Females
Red Males
White Males
88
132
86
WWXX
RWX
WWX Equal Numbers?
• By July 1910, Morgan had accepted the general
Mendelian scheme, but not the notation
• He had accepted the basic chromosome theory of sex
determination, but did not claim W and R were physical
parts of the X chromosome: Only their movements were
correlated with movement of the X
By 1911, however, Morgan had begun to put
all the pieces together:
• Factor for eye color is
physically part of Xchromosome
• Called it “Sex-limited”
• Do not have to assume that
in F1 males R and X always
segregate together, while W
and X never do
• This scheme provided a
mechanistic materialist
basis for Mendelian
inheritance
Adopting A Chromosomal Explanation
Solved 2 Other Problems
• In 1906 Bateson and Punnett had observed 2 Mendelian
anomalies:
- Some characters appeared to be inherited (linked)
together
- But in a small percent of cases, these “linkages” were
disrupted & recombination occurred
• Bateson and Punnett had developed a complex,
philosophically idealist theory to explain these results:
- Attractions
- Repulsions
A Similar Case Occurred in Drosophila
• Body color and wing type
are both sex-linked
• Morgan crossed: Blackvestigial x Yellow-Wild
BV
bv
• F1 Females heterozygous
BbVv, males all bv
• Got 17% recombinants:
Yellow-normal wing &
black body-vestigial wing
•
If these traits are linked
on X-chromsome, how
can we explain this?
Chromosomes Provided an Answer:
• Wilson had shown Morgan a
1909 paper by Belgian
cytologist F.A. Janssens,
hypothesizing chiasmata,
crossing-over of homologous
chromosomes during meiosis
• If Mendelian factors linked on
chromosomes, and
• If homologous chromosomes
somehow exchanged parts
during synapsis,
• Then . . . Linkage could be
broken and recombination could
occur
[Janssen’s Chiasmatype Theory:, La
Cellule 25 (1909): p. 412]
Morgan Used Janssen’s Theory To
Develop A New Technique:
Chromosome Mapping
• If frequency of crossingover is a function of
distance of two factors
apart on the chromosome,
• If crossing-over is
random event,
• Then . . . Cross-over
frequencies in phenotypes
of dihybrid crosses is a
function of the relative
distance apart of factors
on the chromosome
Morgan Explained this Idea to An
Undergrad Student, A.H. Sturtevant
(1890-1970) Working in His Labortory
• That same day, Sturtevant
analyzed data already
collected on 5 sex-linked
factors in Drosophila (3
shown here)
[From John A. Moore, Heredity and Development (N.Y. Oxford, 1963: 104]
• This became the firstever chromosome map 
[Sturtevant, Journal of Experimental Zoology
14 (1913): 43-59]
[From Sturtevant, Journal of Experimental Zoology 14 (1913): 43-59]
The Group Approach
• The Morgan group
worked as a collective
team
- Everyone participated in
planning the experiments
and discussing the results
as shown here during a
Woods Hole summer “lab
meeting”
• Such informality was
unheard of in Europe
MBL 1920
Columbia, 1919
Meanwhile, Many New Types of
Mutants Turned Up in Cultures
Top left: Bridges & Morgan, “Third Chromosome Group…” (Carnegie
Institution of Washington, 1923), Pl I. Bottom, left: Morgan, Evolution
and Genetics (Princeton, 1925): p. 97; Right, Morgan & Bridges, “Sexlinked Inheritance . . .” (Carnegie Institution of Washington, 1916): Pl II
As Mutations Were Mapped There Turned
Out to be As Many Linkage Groups as
there were Chromosome Pairs
• Number of genes was
roughly proportional
to size of each
chromosome pair
• This turned out to be
compelling evidence
that genes were really
physical parts of the
chromosomes
Outline
I.
Introduction: The Importance of History and
Philosophy in Teaching Scientific Methodology
A.
“Should History of Science Be Rated X?”
B.
History and Philosophy of Science are
complementary but they are not the same
II. Logic of Science: What It Can Teach
III. The Case History Method
A.
Development of the Mendelian-Chromosome
Theory of Heredity (MCTH)
B. Methodological Points
C. Extensions to Social/Political Context
Some Principles of “Scientific Method”
Derived from this Case Study
• Often slow and halting way in which new ideas
develop
• Discover one phenomenon (small-scale mutations)
while looking for another (species-level mutations)
• Biases: Difficulty in giving up old ideas
• Philosophical issues:
- Mechanistic materialism - atomization of genes
- Reductionism
- Deduction and hypothesis testing
Methodological Issues Based on the MCTH
• Importance of observation (learning to “see” Ychromosome, new mutations)
• Role of model organisms:
- How do we learn to handle them in the
laboratory?
- Are they representative?
- By breeding them do we “construct” what we
expect to see?
• New paradigms can create blinders: Morgan’s
group put aside any attempt to study the
embryological side of heredity
The Social Construction of Knowledge:
Discrete Nature of Heredity
• Commitment to the
discrete, atomistic gene
meant choosing most
distinct forms of each
strain
• Mutant strains were
“constructed” over the
years to show sharp
discontinuities
• Continuous or
discontinuous series of
eye colors in Drosophila?

Mendelian-Chromosome Theory As A
Kuhnian Revolution & Interfield Theory
• Interfield Theory (Darden-Maul, 1977):
Combining the cytological tradition of
chromosome study with Mendelian breeding data
provided independent evidence for each
• Kuhnian Revolution (1962): The MCTH
represented the expansion of a paradigm
(Mendelism) while solving a number of existing
problems and revealing a whole new set of
research problems
Puzzles, Articulations and New Problems
• Puzzle-Solving:
- Linkage and recombination
- Chromosome aberrations such as deletions or inversions
• Articulations:
- Mapping the chromosomes / linkage maps
- Determining physical location of genes on chromosomes
• New Horizons:
- Position effect: Changes in gene expression based on
position of genes on chromosomes
- Lateral gene transfer (“jumping genes”)
Outline
I.
Introduction: The Importance of History and
Philosophy in Teaching Scientific Methodology
A.
“Should History of Science Be Rated X?”
B.
History and Philosophy of Science are
complementary but they are not the same
II. Logic of Science: What It Can Teach
III. The Case History Method
A.
Development of the Mendelian-Chromosome
Theory of Heredity (MCTH)
B. Methodological Points
C. Extensions to Social/Political Context
Societal/Contextual Dimensions:
Eugenics and Agriculture
• Eugenics: Solving social/behavioral problems with
science: “The self-direction of human evolution.”
• Agriculture: Control of seed production via hybridization
Contemporary Genetic-Social Issues
• Such claims tell us about both how genetics is being
taught/understood, and how it can affect social policy