Adaptation Psychology 3106. Introduction Last class we looked at what you might call the ‘historical pathways’ that a behaviour or trait can take Basically,

AdaptationAdaptation

Psychology 3106Psychology 3106

IntroductionIntroduction

Last class we looked at what you might Last class we looked at what you might call the ‘historical pathways’ that a call the ‘historical pathways’ that a behaviour or trait can takebehaviour or trait can take

Basically, how you get from one form to Basically, how you get from one form to anotheranother

You can also look at the adaptive value You can also look at the adaptive value (fitness consequence) of behaviour(fitness consequence) of behaviour

As noted, these are relatedAs noted, these are related

Adaptation: A DefinitionAdaptation: A Definition

An adaptation is a heritable trait that:An adaptation is a heritable trait that: Either spread because of Natural Selection Either spread because of Natural Selection

and has been maintained by selection to the and has been maintained by selection to the preesntpreesnt

OrOr Is currently spreading relative to alternative Is currently spreading relative to alternative

traits, due to Natural Selectiontraits, due to Natural Selection

More AdaptationMore Adaptation

Nice thing about this definition is that it Nice thing about this definition is that it can help us figure out if something is can help us figure out if something is indeed an adaptation.indeed an adaptation.

Does it increase fitness?? That is the Does it increase fitness?? That is the questionquestion

What are the costs and benefits?What are the costs and benefits?

Not all traits are adaptationsNot all traits are adaptations

The conditions that the trait evolved in The conditions that the trait evolved in may not existmay not exist

The trait may be a maladaptive side effect The trait may be a maladaptive side effect of an adaptive traitof an adaptive trait

The trait is a maladaptive expression of The trait is a maladaptive expression of some adaptive traitsome adaptive trait

The trait may be an The trait may be an exaptationexaptation

Measuring FitnessMeasuring Fitness

Sometimes we can get direct measures of Sometimes we can get direct measures of fitness :fitness : Gamete productionGamete production Offspring survivalOffspring survival Rate of copulationRate of copulation Fertilized egg productionFertilized egg production Offspring productionOffspring production Offspring independenceOffspring independence

Measuring FitnessMeasuring Fitness

Often we have to go to indirect measures Often we have to go to indirect measures of fitness :of fitness : Improved locomotionImproved locomotion Improved access to foodImproved access to food Improved survival chancesImproved survival chances Improved access to territoriesImproved access to territories Better territoriesBetter territories

An Example: Mobbing in GullsAn Example: Mobbing in Gulls

When you get near a nesting colony of When you get near a nesting colony of gulls they get pretty angry….gulls they get pretty angry…. Dive bombingDive bombing Swooping Swooping Hitting!Hitting!

A good guess is that this behaviour is an A good guess is that this behaviour is an adaptation for defense of their youngadaptation for defense of their youngBut, as good as it sounds, does mobbing But, as good as it sounds, does mobbing increase fitness?increase fitness?

Mobbing GullsMobbing Gulls

OK, if mobbing is indeed an adaptation OK, if mobbing is indeed an adaptation then, the degree of success experienced then, the degree of success experienced by mobbing gulls in protecting their eggs by mobbing gulls in protecting their eggs should be proportional to the degree to should be proportional to the degree to which predators are actually mobbed.which predators are actually mobbed.Kruuk (1964) tested this prediction.Kruuk (1964) tested this prediction. Placed 10 hen eggs, every 10 m on a line Placed 10 hen eggs, every 10 m on a line

leading from outside to inside a colonyleading from outside to inside a colony The ones outside the colony were more likely The ones outside the colony were more likely

to have been takento have been taken

Kruuuuuuuuuuuuuuuuk (1964)Kruuuuuuuuuuuuuuuuk (1964)

Mobbing in Barn SwallowsMobbing in Barn Swallows

Barn Swallows also mob.Barn Swallows also mob.

Could be self defenseCould be self defense

Could be mating advertisementCould be mating advertisement

Could be an alternative to parental careCould be an alternative to parental care

Shields (1984) placed a stuffed owl near a Shields (1984) placed a stuffed owl near a colony of barn swallows, and took note of colony of barn swallows, and took note of who mobbedwho mobbed

Shields (1984)Shields (1984)

The Comparative MethodThe Comparative Method

Just as with looking at the history of some Just as with looking at the history of some trait, the question of whether a behaviour trait, the question of whether a behaviour is an adaptation or not can be (partially) is an adaptation or not can be (partially) answered with the Comparative Methodanswered with the Comparative Method

We would expect that birds that are cliff We would expect that birds that are cliff nesters would not mob, while those that nesters would not mob, while those that were ground nesters wouldwere ground nesters would

Regardless of relatednessRegardless of relatedness

Convergent and Divergent Convergent and Divergent EvolutionEvolution

This is in fact the This is in fact the casecase

The common The common ancestor of Gulls and ancestor of Gulls and Barn Swallows was Barn Swallows was ages ago!ages ago!

Indeed, some colonial Indeed, some colonial mammals mob!mammals mob!

Optimality ModelsOptimality Models

When does it make sense to use a When does it make sense to use a particular strategy?particular strategy?

When does it make sense to evolve a When does it make sense to evolve a particular strategy?particular strategy?

Look at the costs and benefits, thugh the Look at the costs and benefits, thugh the use of optimality modelsuse of optimality models

Basically looking at costs and benefitsBasically looking at costs and benefits

Optimality ModelsOptimality Models

You might mob some You might mob some of the predators some of the predators some of the time…..of the time…..Top model looks only Top model looks only at costs and benefitsat costs and benefitsBottom model looks Bottom model looks at percentage of at percentage of cautious and daring cautious and daring mobbers, they are mobbers, they are dependent on each dependent on each other!other!

Criticism of the Adaptationist Criticism of the Adaptationist ApproachApproach

Biggest critic was Stephen J. GouldBiggest critic was Stephen J. Gould The only palaeontologist ever to appear on The only palaeontologist ever to appear on

The SimpsonsThe Simpsons

Trait may be maladaptive now, but Trait may be maladaptive now, but adaptive thenadaptive then

The trail may be a maladaptive byproduct The trail may be a maladaptive byproduct of an previously adaptive (or presently of an previously adaptive (or presently adaptive) traitadaptive) trait

More Criticisms by that baseball More Criticisms by that baseball loving commie loving commie

Trait would never have occurred in the Trait would never have occurred in the past, but new wacky conditions make it past, but new wacky conditions make it show up nowshow up now

The trait is less than ‘perfect’ because it is The trait is less than ‘perfect’ because it is constrained by past evolutionary eventsconstrained by past evolutionary events

Take that Dinosaur manTake that Dinosaur man

An assumption of adaptationism is that An assumption of adaptationism is that traits are adaptive, we then test the traits are adaptive, we then test the prediction.prediction.It has never been about perfection Steve, I It has never been about perfection Steve, I don’t know what you readdon’t know what you readThe point is not to be correct, but to be The point is not to be correct, but to be testable and proved wrong. You should testable and proved wrong. You should have paid more attention in Philosophy of have paid more attention in Philosophy of Science class. Science is not Essentialist!Science class. Science is not Essentialist!

ConclusionsConclusions

Don’t be a ‘rabid adaptationist’Don’t be a ‘rabid adaptationist’

Don’t fall for the naturalistic fallacy either!Don’t fall for the naturalistic fallacy either!

Remember, its all about reproductive Remember, its all about reproductive success in the end, so we really need this success in the end, so we really need this approach to test why something evolved.approach to test why something evolved.

This stuff is all intertwined with the stuff on This stuff is all intertwined with the stuff on the historical pathways of evolution that the historical pathways of evolution that we talked about earlierwe talked about earlier