Adaptation Psychology 3106

Introduction Last class we looked at what you might call the ‘historical pathways’ that a behaviour or trait can take Basically, how you get from one form to another You can also look at the adaptive value (fitness consequence) of behaviour As noted, these are related

Adaptation: A Definition An adaptation is a heritable trait that: Either spread because of Natural Selection and has been maintained by selection to the preesnt Or Is currently spreading relative to alternative traits, due to Natural Selection

More Adaptation Nice thing about this definition is that it can help us figure out if something is indeed an adaptation. Does it increase fitness?? That is the question What are the costs and benefits?

Not all traits are adaptations The conditions that the trait evolved in may not exist The trait may be a maladaptive side effect of an adaptive trait The trait is a maladaptive expression of some adaptive trait The trait may be an exaptation

Measuring Fitness Sometimes we can get direct measures of fitness : Gamete production Offspring survival Rate of copulation Fertilized egg production Offspring production Offspring independence

Measuring Fitness Often we have to go to indirect measures of fitness : Improved locomotion Improved access to food Improved survival chances Improved access to territories Better territories

An Example: Mobbing in Gulls When you get near a nesting colony of gulls they get pretty angry…. Dive bombing Swooping Hitting! A good guess is that this behaviour is an adaptation for defense of their young But, as good as it sounds, does mobbing increase fitness?

Mobbing Gulls OK, if mobbing is indeed an adaptation then, the degree of success experienced by mobbing gulls in protecting their eggs should be proportional to the degree to which predators are actually mobbed. Kruuk (1964) tested this prediction. Placed 10 hen eggs, every 10 m on a line leading from outside to inside a colony The ones outside the colony were more likely to have been taken

Kruuuuuuuuuuuuuuuuk (1964)

Mobbing in Barn Swallows Barn Swallows also mob. Could be self defense Could be mating advertisement Could be an alternative to parental care Shields (1984) placed a stuffed owl near a colony of barn swallows, and took note of who mobbed

Shields (1984)

The Comparative Method Just as with looking at the history of some trait, the question of whether a behaviour is an adaptation or not can be (partially) answered with the Comparative Method We would expect that birds that are cliff nesters would not mob, while those that were ground nesters would Regardless of relatedness

Convergent and Divergent Evolution This is in fact the case The common ancestor of Gulls and Barn Swallows was ages ago! Indeed, some colonial mammals mob!

Optimality Models When does it make sense to use a particular strategy? When does it make sense to evolve a particular strategy? Look at the costs and benefits, thugh the use of optimality models Basically looking at costs and benefits

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

Criticism of the Adaptationist Approach Biggest critic was Stephen J. Gould The only palaeontologist ever to appear on The Simpsons Trait may be maladaptive now, but adaptive then The trail may be a maladaptive byproduct of an previously adaptive (or presently adaptive) trait

More Criticisms by that baseball loving commie Trait would never have occurred in the past, but new wacky conditions make it show up now The trait is less than ‘perfect’ because it is constrained by past evolutionary events

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

Conclusions Don’t be a ‘rabid adaptationist’ Don’t fall for the naturalistic fallacy either! Remember, its all about reproductive success in the end, so we really need this approach to test why something evolved. This stuff is all intertwined with the stuff on the historical pathways of evolution that we talked about earlier