2 PoKs in natural science
• ”What we know something to be”
is not necessarily the same as
”What it is”.
• Influence of social-cultural context
on scientists: claims accepted as
knowlege in one context, and
unacceptable in another.
What carries genetic information?
What is its structure?
• Late 1800s: DNA (de-oxyribose nucleic
acid) found in the nucleus (together with
proteins).
• Is DNA the hereditary material? (maybe
proteins are?)
• What is the structure of DNA?
The structure of DNA
Evidence from:
• Biochemistry: phosphate groups, water,
4 different nitrogenous bases in equal
ratios (Chargaff):
Adenine, Thymine
Cytosine, Guanine
Physics, X-Ray diffraction images: a helical
structure (Pauling – nobel laureate – 3
helices).
Watson & Crick (in 1959)
W & C present a first model
• Watson had listened to a presentation by
Rosalind Franklin in which she estimated the
amount of water based on her X-Ray diffraction
patterns. They then built a model and presented
it for peer review.
• But Watson did not take notes, remembered
incorrectly, and when Franklin saw the model,
her comments falsified it immediately.
• 1953: a revised model ..
The original model (1953)
DNA structure
Biochemistry: bases in equal ratios
W & C: what can this mean?
Ce n est pas un pipe ..
The map is not the territory,
the thing is not the thing named.
Bateson
Methods of verification .. The
inevitability of uncertainty
T. S. Eliot, The Hollow Men
Between the idea and the reality;
between the motion and the act,
Falls the shadow.
Between the conception and the creation;
between the emotion and the response,
Falls the shadow.
Binomial system of nomenclature
• Carolus Linneaus (1707-1778).
• Kingdom (Animalia), Phylum (Vertebrata),
Class (Mammalia), Order (Primates)
(genus) Homo, (species) sapiens
While modified, remains the standard over 200 yrs.
Humans classified into sub-groups:
• Within Homo sapiens Linneaus proposed four
taxa: americanus, asiaticus, africanus,
europeanus, each race with characteristics
endemic to individuals belonging to it:
Native Americans: reddish, stubborn, anger easily.
Africans: black, relaxed, negligent.
Asians: yellow, avaricious, easily distracted.
Europeans: white, gentle, and inventive.
Linneaus now regarded as a father of
scientific racism; subspecies (race) rejected.
J. Marks, U. Calif. (1999) personal.uncc.edu/.../aaa/marksaaa99.htm
• “The claim that we are apes is not a fact of
nature, but an artifact of the way we organize
and divide nature”.
• “As a consequence, that claim has a lot more to
do with the work of Durkheim and Mauss than
with Darwin and Huxley. This is an obvious site
for a biological anthropology – a field both
anthropologically-informed and biologically
meaningful. And it’s vacant at the moment. “