Lecture 3

1.1. Leftovers…Leftovers…

2.2. Kinds of evidence and reasoning at work in Kinds of evidence and reasoning at work in evolutionary theorizing.evolutionary theorizing.

3.3. Anticipating next readings (by A.J. Ayer and Anticipating next readings (by A.J. Ayer and Karl Popper) and topic.Karl Popper) and topic.

4.4. Introduction to Introduction to The Elegant UniverseThe Elegant Universe (film (film today)today)

Leftovers

The evidence for subatomic particles – and The evidence for subatomic particles – and the same turns out to be true for evidence for the same turns out to be true for evidence for evolutionary processes and events – is evolutionary processes and events – is indirectindirect

We draw inferences from what we can We draw inferences from what we can observe to what we cannotobserve to what we cannot

Leftovers

We bring metaphysical or ontological We bring metaphysical or ontological assumptions about what there is and about assumptions about what there is and about causes at workcauses at work

We bring epistemological assumptions about We bring epistemological assumptions about the nature and limits of our knowledge in a the nature and limits of our knowledge in a given domain – including what justifies the given domain – including what justifies the way we are reasoning, our technology, etc.way we are reasoning, our technology, etc.

We bring aesthetic (and quasi-metaphysical) We bring aesthetic (and quasi-metaphysical) assumptions: e.g., that the universe is simple assumptions: e.g., that the universe is simple or elegantor elegant

Leftovers

For a great episode on the discovery of and For a great episode on the discovery of and years of work to put Ardi together:years of work to put Ardi together:

www.pbs.org/newshour/videoswww.pbs.org/newshour/videos For a great read every Tuesday:For a great read every Tuesday:

www.nytimes.comwww.nytimes.com: Science Times: Science Times How did Lucy get her name?How did Lucy get her name?

Evolutionary theorizingEvolutionary theorizing

The late great Stephen Jay The late great Stephen Jay GouldGould

(1941-2002)(1941-2002)

Harvard paleontologist and Harvard paleontologist and evolutionary theoristevolutionary theorist

One of the strongest defenders One of the strongest defenders of Darwin and evolutionary of Darwin and evolutionary theorytheory

One of the strongest critics of One of the strongest critics of some aspects of some aspects of evolutionary theory.evolutionary theory.

Natural SelectionNatural Selection

Darwin’s “great discovery”Darwin’s “great discovery” A A mechanism by which evolution could occurmechanism by which evolution could occur.. Similar to the revolution that brought us “Continental Drift” Similar to the revolution that brought us “Continental Drift”

given the mechanism of “Plate Tectonics” …given the mechanism of “Plate Tectonics” …

What it is…What it is… 1. There is intra-species variation.1. There is intra-species variation. 2. There is a struggle for existence.2. There is a struggle for existence. 3. If some variation provides an advantage (however small…) 3. If some variation provides an advantage (however small…)

in terms of survival and/or reproductive success, those in terms of survival and/or reproductive success, those organisms with it will organisms with it will tendtend toto survive better and reproduce survive better and reproduce more successfully more successfully and tendand tend toto pass on the trait to their pass on the trait to their offspring. offspring.

The Likelihood PrincipleThe Likelihood Principle

OO: an observation or set of observations: an observation or set of observations

HH: a hypothesis proposed as an explanation of : a hypothesis proposed as an explanation of OO

The likelihood principle asks The likelihood principle asks

““What is the likelihood of What is the likelihood of O (observations) O (observations) given given H (hypothesis)H (hypothesis)?”?”

P(P(OO//HH))

NOTNOT “What is the probability of “What is the probability of HH given given OO??

P(P(HH//OO))

The Likelihood PrincipleThe Likelihood Principle

OO: There is noise in the attic.: There is noise in the attic.

HH: Gremlins are bowling in the attic.: Gremlins are bowling in the attic.

““What is the likelihood of What is the likelihood of O O given given HH?”?”

P(P(OO//HH))

VERY HIGH!VERY HIGH!

““What is the probability of What is the probability of HH given given OO??

P(P(HH//OO))

VERY LOW (if any probability at all)!

Paley’s argument from designPaley’s argument from design

OO: Organisms are perfectly fit relative to their : Organisms are perfectly fit relative to their environments, and their parts (e.g., eyes) are environments, and their parts (e.g., eyes) are perfectly designed for their functions.perfectly designed for their functions.

HH1: Organisms and their parts were produced by : Organisms and their parts were produced by a a DesignerDesigner..

HH22: Organisms and their parts are the result of : Organisms and their parts are the result of random, physical processesrandom, physical processes..

““Obviously”, Paley concluded,Obviously”, Paley concluded,P(O/HP(O/H11)) >> >> P(O/HP(O/H22))

The likelihood of The likelihood of OO is is much highermuch higher if H if H11 than if than if HH22..

Paley’s reasoning updated…Paley’s reasoning updated…

OO: : Organisms are perfectly fit to their environments and Organisms are perfectly fit to their environments and their parts (e.g., eyes) are perfect designed for their their parts (e.g., eyes) are perfect designed for their functions.functions.

No. It turns out there are many imperfections, and a No. It turns out there are many imperfections, and a change in environment can easily wipe out a population change in environment can easily wipe out a population or species however well suited they were to an earlier or species however well suited they were to an earlier environmentenvironment

HH11: All was produced by a : All was produced by a DesignerDesignerHH22: All are the results of random, physical changes: All are the results of random, physical changesPaley could only think of Paley could only think of twotwo possibilities but now we possibilities but now we

have:have:HH33: : Natural selection, which doesn’t require supernatural Natural selection, which doesn’t require supernatural

intervention and is also intervention and is also notnot randomrandom..

Paley’s reasoning updated…Paley’s reasoning updated…

Not random?Not random? After all, mutations are often random… and After all, mutations are often random… and

they underlie they underlie phenotypic/morphological/behavioral phenotypic/morphological/behavioral change…change…

True, but NS is not True, but NS is not itselfitself a random process. a random process. Consider it to be an algorithm…Consider it to be an algorithm… Like long division?Like long division? No.No. More like an elimination tournament in tennis.More like an elimination tournament in tennis.

The Panda’s ThumbThe Panda’s Thumb

OO: the panda’s “thumb” (TPT) and what it actually : the panda’s “thumb” (TPT) and what it actually is (an enlarged wrist bone)is (an enlarged wrist bone)

HH11: TPT came about through natural selection: the : TPT came about through natural selection: the (blind) tinkering with available parts that gave (blind) tinkering with available parts that gave those ancestors with it an advantage and, thus, those ancestors with it an advantage and, thus, the trait spread.the trait spread.

HH22: TPT was designed by perfect engineer.: TPT was designed by perfect engineer.

Gould:Gould:

P(P(OO//HH11) >> P() >> P(OO//HH22))

The Panda’s ThumbThe Panda’s Thumb

Gould: Gould: P(P(OO//HH11) >> P() >> P(OO//HH22))WhatWhat is the evidenceis the evidence??Comparative anatomy:Comparative anatomy:Both the radial sesamoid, which in its elongated Both the radial sesamoid, which in its elongated

form constitutes this false “digit”, and the form constitutes this false “digit”, and the relevant musculature that gives the digit its relevant musculature that gives the digit its relative relative rigidness and rigidness and relative relative flexibility, are flexibility, are common to other species, including other bears.common to other species, including other bears.

The (perhaps single) genetic change producing a The (perhaps single) genetic change producing a larger radial sesamoid, would given their spatial larger radial sesamoid, would given their spatial locations, force the change in the musculature. locations, force the change in the musculature.

The Panda’s ThumbThe Panda’s Thumb

Gould: Gould: P(P(OO//HH11) >> P() >> P(OO//HH22))

WhatWhat is the evidenceis the evidence??

Comparative anatomy:Comparative anatomy:

In many other bears, the radial sesamoid is also In many other bears, the radial sesamoid is also somewhat enlarged.somewhat enlarged.

This is by no means a “perfect” thumb (it is neither This is by no means a “perfect” thumb (it is neither opposable nor able to manipulate objects by opposable nor able to manipulate objects by itself).itself).

It is, rather, the result of tinkering with parts It is, rather, the result of tinkering with parts available to the panda’s ancestors.available to the panda’s ancestors.

Darwin’s orchidsDarwin’s orchids

Non-sexual reproduction is cheaper, but sexual Non-sexual reproduction is cheaper, but sexual reproduction insures that an organism’s progeny reproduction insures that an organism’s progeny are varied (and thus will have a better chance of are varied (and thus will have a better chance of survival if conditions change).survival if conditions change).

From the same relatively primitive petal of its From the same relatively primitive petal of its ancestor, varieties of orchids have different ancestor, varieties of orchids have different “contraptions” for insuring cross-pollination“contraptions” for insuring cross-pollination

QWERTY PHENOMENAQWERTY PHENOMENA

Like the arrangements of the keys on a keyboard, Like the arrangements of the keys on a keyboard, QWERTY phenomena are phenomena that show QWERTY phenomena are phenomena that show signs of history: a history of R&D (research and signs of history: a history of R&D (research and development) using what’s available, and limited development) using what’s available, and limited or directed by contingencies and constraints… or directed by contingencies and constraints… Francis Crick called them “frozen accidents”Francis Crick called them “frozen accidents”

QWERTY phenomena abound in the organic QWERTY phenomena abound in the organic world.world.

QWERTY PHENOMENA

In our case:In our case:wisdom teeth, the blank spot in the center of each of our wisdom teeth, the blank spot in the center of each of our eyes, the possibility of retinal detachment, our “tail eyes, the possibility of retinal detachment, our “tail bone”, our back problems, (perhaps) our appendix, bone”, our back problems, (perhaps) our appendix, relatively short gestational period, male nipples….relatively short gestational period, male nipples….

Other cases:Other cases:blind fish in dark caves, with eyes that don’t function, blind fish in dark caves, with eyes that don’t function, but whose ancestors had functioning eyesbut whose ancestors had functioning eyesblind fish in dark caves, without eyes, whose ancestors blind fish in dark caves, without eyes, whose ancestors did have eyesdid have eyes““toothless” species of whales in which embryos have toothless” species of whales in which embryos have teeth and lose them during natal developmentteeth and lose them during natal development

Part IIIPart III

Next readingsNext readings

What distinguishes science from pseudo-science?What distinguishes science from pseudo-science?

Logical Positivism:Logical Positivism: Science should and must be a positive force for Science should and must be a positive force for

human wellbeing human wellbeing Logical Empiricism (same movement):Logical Empiricism (same movement):

Working to identify the role of logic and that of Working to identify the role of logic and that of experience in the workings of experience in the workings of genuinegenuine science. science.

Both emphases underlie the work to identify the Both emphases underlie the work to identify the criterion (or criteria) that demarcate science (i.e., criterion (or criteria) that demarcate science (i.e., distinguish it from) “pseudo-science” and “non-distinguish it from) “pseudo-science” and “non-science”.science”.

What distinguishes science from pseudo-science?

A.J. Ayer (first reading)A.J. Ayer (first reading) A Logical Positivist (aka Logical Empiricist)A Logical Positivist (aka Logical Empiricist) His target as “pseudo-science” (“nonsense” or His target as “pseudo-science” (“nonsense” or

without meaning): statements that cannot be without meaning): statements that cannot be verifiedverified by experience.by experience.

He terms them ‘metaphysical’ but as he uses it, the He terms them ‘metaphysical’ but as he uses it, the term has a different sense than that we discussed as term has a different sense than that we discussed as “philosophical metaphysics or ontology”“philosophical metaphysics or ontology”

It concerns efforts to identify a reality that allegedly It concerns efforts to identify a reality that allegedly “transcends” our experiences.“transcends” our experiences.

His criterion: verifiabilityHis criterion: verifiability

What distinguishes science from pseudo-science?

Sir Karl Popper (second reading)Sir Karl Popper (second reading) Rejects “Verifiabiliity” (too many pseudo-Rejects “Verifiabiliity” (too many pseudo-

scientific theories can be claimed to “fit” the scientific theories can be claimed to “fit” the evidence)evidence)

Offers “Falsifiability” as an alternative criterion Offers “Falsifiability” as an alternative criterion

Part IVPart IV

The Elegant UniverseThe Elegant Universe

The Elegant UniverseThe Elegant Universe

Note the title! The universe is “elegant”!Note the title! The universe is “elegant”! String Theory: everything there is is made of String Theory: everything there is is made of

tiny vibrating strings of energy… (tiny vibrating strings of energy… (notnot some some one or more particles!)one or more particles!)

Goals: a grand theory of Goals: a grand theory of everythingeverything!! UnifyingUnifying physics physics

Resolving the contradictions between the 2 pillars Resolving the contradictions between the 2 pillars of contemporary physics:of contemporary physics:

Quantum theoryQuantum theory RelativityRelativity