Download Apr. 7

Lecture 3
1.
2.
3.
Kinds of evidence and reasoning at work in
evolutionary theorizing.
Anticipating next readings (by A.J. Ayer and
Karl Popper) and topic.
Introduction to “The Mind’s Big Bang”
The Likelihood Principle
O: an observation or set of observations
H: a hypothesis proposed as an explanation of O
The likelihood principle asks “What is the
likelihood of O (observations) given H
(hypothesis)?”
P(O/H)
NOT “What is the probability of H given O?
P(H/O)
The Likelihood Principle
O: There is noise in the attic.
H: Gremlins are bowling in the attic.
“What is the likelihood of O given H?”
P(O/H)
VERY HIGH!
“What is the probability of H given O?
P(H/O)
VERY LOW (if probable at all)!
Paley’s argument from design
O: Organisms are perfectly fit to their
environments and their parts (e.g., eyes) are
perfectly designed for their functions.
 H1: Organisms and their parts were produced by
a Designer.
 H2: Organisms and their parts are the result of
random, physical processes.
 “Obviously”, Paley concluded,
P(O/H1) >> P(O/H2)
 The likelihood of O is much higher if H1 than if
H 2.

Paley’s reasoning updated…
O: Organisms are perfectly fit to their environments and
their parts (e.g., eyes) are perfect designed for their
functions.
Turns out there are many imperfections, and a change in
environment can easily wipe out a population or
species…
H1: All was produced by a Designer
H2: All are the results of random, physical changes
Paley could only think of two possibilities but now we
have:
H3: Natural selection, which doesn’t require supernatural
intervention and is also not random.
The Panda’s Thumb
O: the panda’s “thumb” (TPT) and what it actually
is (an enlarged wrist bone)
H1: TPT came about through natural selection: the
(blind) tinkering with available parts that gave
those ancestors with it an advantage and, thus,
the trait spread.
H2: TPT was designed by perfect engineer.
Gould:
P(O/H1) >> P(O/H2)
The Panda’s Thumb
Gould: P(O/H1) >> P(O/H2)
What is the evidence?
Comparative anatomy:
Both the radial sesamoid, which in its elongated
form constitutes this false “digit”, and the
relevant musculature that gives the digit its
relative rigidness and relative flexibility, are
common to other species, including other bears.
The (perhaps single) genetic change producing a
larger radial sesamoid, would given their spatial
locations, force the change in the musculature.
The Panda’s Thumb
Gould: P(O/H1) >> P(O/H2)
What is the evidence?
Comparative anatomy:
In many other bears, the radial sesamoid is also
somewhat enlarged.
This is by no means a “perfect” thumb (it is neither
opposable nor able to manipulate objects by
itself).
It is, rather, the result of tinkering with parts
available to the panda’s ancestors.
Darwin’s orchids
Non-sexual reproduction is cheaper, but sexual
reproduction insures that an organism’s progeny
are varied (and thus will have a better chance of
survival if conditions change).
 From the same relatively primitive petal of its
ancestor, varieties of orchids have different
“contraptions” for insuring cross-pollination
(insuring that insects lured by their nectar are
also coated in pollen that they will in turn pass
on to the next female orchid they visit…)

QWERTY PHENOMENA
Like the arrangements of the keys on a keyboard,
QWERTY phenomena are phenomena that show
signs of history: a history of R&D (research and
development) using what’s available, and limited
or directed by contingencies and constraints…
Francis Crick called them “frozen accidents”
QWERTY phenomena abound in the organic
world.
QWERTY PHENOMENA
In our case:
wisdom teeth, the blank spot in the center of each of our
eyes, the possibility of retinal detachment, our “tail
bone”, our back problems, (perhaps) our appendix,
relatively short gestational period, male nipples….
Other cases:
blind fish in dark caves, with eyes that don’t function,
but whose ancestors had functioning eyes
blind fish in dark caves, without eyes, whose ancestors
did have eyes
“toothless” species of whales in which embryos have
teeth and lose them during natal development
What distinguishes science from
pseudo-science? And why care?
The emergence of the philosophy of science in
the 1920s in Europe
 The Vienna Circle
 Logical Positivism (aka Positivism or Logical
Empiricism)
 Reacting to 2 significant developments:

 The
eclipsing of Newtonian physics by Special and
General Relativity
 The growing menace of Fascism, anti-Semitism, and
the so-called scientific theories put forward by Nazis
What distinguishes science from pseudo-science?

Logical Positivism:
 Science
should and must be a positive force for
human wellbeing

Logical Empiricism (same movement):
 Working
to identify the role of logic and that of
experience in the workings of genuine science.

Both emphases underlie the work to identify the
criterion (or criteria) that demarcate science (i.e.,
distinguish it from) “pseudo-science” and “nonscience”.
What distinguishes science from pseudo-science?






A.J. Ayer (first reading)
A Logical Positivist (aka Logical Empiricist)
His target as “pseudo-science” (“nonsense” or
without meaning): statements that cannot be verified
by experience.
He terms them ‘metaphysical’ but as he uses it, the
term has a different sense than that we discussed as
“philosophical metaphysics or ontology”
It concerns efforts to identify a reality that allegedly
“transcends” our experiences.
His criterion: verifiability
What distinguishes science from pseudo-science?
Sir Karl Popper (second reading)
 Rejects “Verifiabiliity” (too many pseudoscientific theories be claimed to “fit” the
evidence)
 Offers “Falsifiability” as an alternative criterion
 Simply put: a statement, hypothesis, or theory is
scientific only if it is, in principle, falsifiable
 There are things it prohibits, which if they were
to occur or be observed, would show the
hypothesis or theory in question to be false.

The Mind’s “Big Bang”

When and how did the human brain emerge?
 A single
mutation?
 Gradually?
What kinds of evidence do scientists appeal to in
“reconstructing” the event?
 The method of “reverse engineering”

 Drawing
inferences based on what we can observe
(by way of traits and artifacts) to historical episodes
 DNA analysis, paleontology, anthropology,
archaeology
The Mind’s “Big Bang”
When and how did the human brain emerge?
 What kinds of evidence do scientists appeal to in
“reconstructing” the event?
 Consider the evidence discussed in the film. Do
you find some inferences more compelling than
others? If so, why…

 Cave
paintings
 Tools
 Beads
 Graves…