Lecture 5: Adaptationism, part 1

1. Review: summary of the discussion from case studies; G& L’s claims; refining the claims.

2. Evaluating empirical adaptationism: comparative monism versus pluralism.

– A bad way to pose the question of the comparative significance of NS.

– Some remarks on constraints: how not to make adaptationism obviously false.

3. Methodological adaptationism– Physical, design and intentional stances– Research programs and falsifiability.

Discussion of examples of bad adaptationist arguments elicited key moves of rejoinder

• Claim about “optimality” will be silly unless we recognize constraints (butterfly machine guns). Good adaptationists will recognize constraints. (call for better practice)

• Claim that “just so” stories are easy to cook up but hard to confirm doesn’t show they can’t be confirmed (call for better practice) Possible ad hominem: anti-adaptationist stories can be “cooked up” too.

• Critiques of bad adaptationist arguments are operating against background of adaptationist assumptions.

[Review of slides 6 & 7 from lecture 4]

Adaptive/adaptation

Adaptive: contributing positively to the current fitness of the organism that possess it

Adaptation: a feature whose presence today can be explained by the fact that its presence served some useful purpose in previous generations and hence contributed to the reproductive fitness of organisms who possessed it.

Some adaptations are not adaptive: appendix (Foreshadowing: Singer on our moral emotions.)

Some adaptive traits are not adaptations: reading (S&G)

Understanding Empirical Adaptationism

Sober’s explanation of the empirical adaptationist/anti-adaptationist disagreement (in Hull and Ruse, 1998, on reserve):

Analogy: falling objects (on earth) accelerate downward at a rate of 9.8/second2.unless subject to countervailing forces.

In a population subject to natural selection fitter traits become more common and less fit traits become more rare, unless some other force prevents this from happening (e.g drift)

Adaptationists: comparative monists about evolutionary forces; non-adaptationists are comparative pluralists.

Analogy: are organisms mostly more like bowling balls than like feathers? What idealizations will work?

A bad way to ask about the relative significance of NS (Sober)

• Consider the variant that evolves, say P1

• Ask what conceivable variations there are: P1…Pn…Pn+m

• Make a hypothesis about the variations that were actually available in the ancestral population (i.e. winnow (2) down with knowledge about mechanical and other constraints) to get the set: P1… Pn

• Compare the strength of NS and the strength of other forces by comparing the size of the reduction from n variants to the one that evolved, to the size of the reduction between n+m and n. This is conceptually confused: m depends on our imaginations!

On “Optimality”

G&L accuse adaptationists of thinking NS optimizes (and responding to putative conflicting data by positing unforeseen constraints). Adaptationist position is silly unless claim about optimization is made relative to a set of assumed background constraints; e.g. mechanical, developmental, genetic.

Fittest phenoptype may not be available for NS to choose. Simple example (Maynard Smith): leg length, leg strength,

and running speed. Best outcome with long, strong legs, but length and strength must be traded off. Task is to find the best solution to this tradeoff.

Summary of the debate over EA

• Distinguish the truth of empirical adaptationism from the truth of any particular adaptationist explanation. Particular adaptationist hypotheses can be well or ill supported; assumptions about constraints can be well or ill motivated.

• EA is highly general empirical claim: the jury is out on it.

• Defuse some of the fuss by mounting particular critiques of e.g. sociobiology inferences.

• It may be best to locate a range of positions: relatively more or less pluralist. (If so debate may be hotter than it is deep.)

Methodological Adaptationism

Key questions:

2. How useful is adaptationist thinking?

3. Are G&L right to charge adaptationists with making their view unfalsifiable?

4. Would that make it bad science?

5. How do we evaluate research heuristics?

On usefulness: intentional, design and physical stances (Dennett)

Dennett: adaptationist thinking is indispensible. It amounts to adopting the intentional stance towards “mother nature” and it massively reduces complexity of prediction.

The physical stance: predict the behavior of an entity using knowledge of its physical constitution and the laws of physics.

The design stance: assume that the entity in question has been designed in a certain way and predict that it will behave as designed.

The intentional stance: attempt to explain and predict an entity’s behavior by treating it as if it were a rational agent whose actions are governed by its beliefs and desires.

Intentional stance in biological explanation

We call on insights from the intentional stance to understand artifacts:• figure out what the designers had in mind• see the object as a product of “reasoned design

development, choices among alternatives, in which the decisions reached were deemed best by the designers”

• Making assumptions about the reasons for the presence of their parts. (Dennett 230)

Analogy in biology: organisms as designed, analogously with artifacts. But no designer. Intentional metaphors; e.g. “reason,” “in order to.” Metaphors are ok, but they can mislead (danger greatest when talking about creatures with a psychology)

Falsifiability and research programs

Theories do not face the court of experience in isolation: before they generate claims about observations they must be combined with auxiliary hypotheses.

T+A1…An --> O; from not-O can only infer the falsity of the set of T+A1…An. Nothing in principle wrong with laying the blame elsewhere as e.g. happens when a biologist posits an unforeseen constraint.

A research heuristic such as “look for good design, keep looking” is not an empirical claim at all. It can’t be falsified, but it can be evaluated by its fecundity.