Lecture 3 1. Leftovers… 2. Kinds of evidence and reasoning at work in evolutionary theorizing. 3. Anticipating next readings (by A.J. Ayer and Karl Popper) and topic. 4. Introduction to The Elegant Universe (film today)

Leftovers  The evidence for subatomic particles – and the same turns out to be true for evidence for evolutionary processes and events – is indirect  We draw inferences from what we can observe to what we cannot

Leftovers  We bring metaphysical or ontological assumptions about what there is and about causes at work  We bring epistemological assumptions about the nature and limits of our knowledge in a given domain – including what justifies the way we are reasoning, our technology, etc.  We bring aesthetic (and quasi-metaphysical) assumptions: e.g., that the universe is simple or elegant

Leftovers  For a great episode on the discovery of and years of work to put Ardi together:  For a great read every Tuesday: Science Times  How did Lucy get her name?

Evolutionary theorizing The late great Stephen Jay Gould ( ) Harvard paleontologist and evolutionary theorist One of the strongest defenders of Darwin and evolutionary theory One of the strongest critics of some aspects of evolutionary theory.

Natural Selection  Darwin’s “great discovery”  A mechanism by which evolution could occur.  Similar to the revolution that brought us “Continental Drift” given the mechanism of “Plate Tectonics” …  What it is…  1. There is intra-species variation.  2. There is a struggle for existence.  3. If some variation provides an advantage (however small…) in terms of survival and/or reproductive success, those organisms with it will tend to survive better and reproduce more successfully and tend to pass on the trait to their offspring.

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 any probability at all)!

Paley’s argument from design  O: Organisms are perfectly fit relative to their environments, and their parts (e.g., eyes) are perfectly designed for their functions.  H: Organisms and their parts were produced by a Designer.  H 1 : Organisms and their parts were produced by a Designer.  H 2 : Organisms and their parts are the result of random, physical processes.  “Obviously”, Paley concluded, P(O/H 1 ) >> P(O/H 2 )  The likelihood of O is much higher if H 1 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. No. It turns out there are many imperfections, and a change in environment can easily wipe out a population or species however well suited they were to an earlier environment H 1 : All was produced by a Designer H 2 : All are the results of random, physical changes Paley could only think of two possibilities but now we have: H 3 : Natural selection, which doesn’t require supernatural intervention and is also not random.

Paley’s reasoning updated…  Not random?  After all, mutations are often random… and they underlie phenotypic/morphological/behavioral change…  True, but NS is not itself a random process.  Consider it to be an algorithm…  Like long division?  No.  More like an elimination tournament in tennis.

The Panda’s Thumb O: the panda’s “thumb” (TPT) and what it actually is (an enlarged wrist bone) H 1 : 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. H 2 : TPT was designed by perfect engineer. Gould: P(O/H 1 ) >> P(O/H 2 )

The Panda’s Thumb Gould: P(O/H 1 ) >> P(O/H 2 ) 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/H 1 ) >> P(O/H 2 ) 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

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

Part III Next readings

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 “non- science”.

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 pseudo- scientific theories can be claimed to “fit” the evidence)  Offers “Falsifiability” as an alternative criterion

Part IV The Elegant Universe

 Note the title! The universe is “elegant”!  String Theory: everything there is is made of tiny vibrating strings of energy… (not some one or more particles!)  Goals: a grand theory of everything!  Unifying physics  Resolving the contradictions between the 2 pillars of contemporary physics:  Quantum theory  Relativity