Week 2 - evolutionary histories

analogies

convergent evolution - independent evolution that produces analogous traits (evolve by themselves but look the same) e.g. bird and bat wings

homologies

adaptive radiation - traits are similar by descent e.g. human arm and cat foot

how can you tell the difference between analogous and homologous traits?

comparative method - phylogenetic history and ecological pressures

vestigial traits

traits that still exist, but have lost their function through evolution (e.g. tail bone)

behavioural vestigial characteristics

phobias, e.g. spiders and snakes even though its rare to be bitten by one here

what are 4 ways in which traits are not adaptive

exaptation

developmental byproducts

maladaptions

phylogenic inertia

Exaptations

traits that serve a different purpose than the one they were adapted for (also called pre-adaptions or co-opted traits) e.g. feathers for flight initially for insulation or to show off.

Developmental byproducts

or ‘correlated byproduct’ - traits that arise as a byproduct for a selected trait somewhere else (e.g. men having nipples even though they cba to breastfeed)

maladaptions

traits can be adaptive in the environment in which they evolved (e.g. EEA) but now e.g. preferences for sugar and fat which would’ve helped us when it was not super abundant

Phylogenic inertia

not all traits can evolve, limits on what can evolve due to previous adaptions, genetic and physical constraints on what can evolve - e.g. we only have 4 limbs so couldn’t evolve 2 more for wings

Pan-adaptationist thinking

belief that all traits are adaptive and there for their function

how are design solutions a misunderstanding of evolution?

Orgel’s second rule, evolution is smarter than you - inability to explain traits doesn’t negate their existence

how in inevitability a misunderstanding of evolution?

The species and traits (e.g. complexity) are not destined, outcomes can be very different

how is evolution being ‘for the good of the species’ a misunderstanding?

for the good of the gene rather than the species - on average, evolution needs to increase fitness in order to have more copies of the genome being passed on

‘is-ought fallacy’ misunderstanding of evolution

Hume’s law; distinction between normative statement ‘is’ and moral statement ‘ought’ . just because something did evolve, doesn’t mean we ‘ought’ to act that way e.g. men usually taller, also the ‘adaptive’ function of rape - not right

naturalistic fallacy

goodness/morality cannot be reduced to natural properties, desires, pleasures etc. (Moore, 1903) - e.g. eating donuts feels good, doesnt mean it is

how is nature/nurture a false dichotomy

genes AND environment influence almost every phenotype

social spencerism

Herbert Spencer - ‘survival of the fittest’ - should apply to economies

eugenics

Galton (1883) - breed desired traits into a population (or undesired ones out) - misuse

the role of sociobiology in evolution

E.O. Wilson (1975) took the evolutionary approach of ethologists, but focused on function (ultimate explanation) rather than stimuli (proximate)

• e.g. SSSM (Standard social sciences model) sees humans as a blank slate and all human behavior as leant ( e.g. Mead - differences in cultures isn’t explained by biology.

Criticized for its reductionism and biological determinism

what is evolutionary psychology

evolutionary psychology arose in response to criticisms to sociobiology .

• we evolved solutions to ancestral adaptive problems, selections for evolved psychological mechanisms (not behaviour)

what do Tooby & Cosmides suggest about evolutionary psychology

‘the adapted mind’ - we have modular and adaptive psychological mechanisms - domain specific ‘mental organs’

• Fodor : modularity of the mind e.g. different areas for language tasks

what are some universal psychological adaptive traits? (5)

• experience and expression of emotions

• spoken language

• status and roles including division of labour

• incest avoidance

• developmental trajectories

What is the EEA?

Environment of evolutionary adaptedness

discuss the EEA

environment of evolutionary adaptiveness - in the African Savannah, where we evolved from (during the pleistoscene) - 99% of the evolutionary history of homo.

• evolutionary mismatch, or adaptive lag - maladaptions can be seen as a result of adaptions from the EEA (e.g. phobias of spiders)

critiques of evolutionary psychology

it didn’t change much from sociobiology, has panadaptionist thinking and ‘just-so’ storytelling elements.

• the concept is limited as little is known about the EEA

• cognitive abilities may be byproducts of more general abilities

• cognition involves integration across domains

• human universals overlook important variation e.g. sexual selection influenced by sex-based mortality, population density and variation in mate quality

define behavioral ecology

studies adaptive responses to local environment (as opposed to EEA), how optimality and life history adapted from behavioral ecology - how do differences among individuals change due to fitness/optimality explanations

• not interested in proximate mechanisms (e.g. psychology)

• may use historical data sets to see how environment influences population level behavior.

facultative/obligative behaviour

• facultative: can do (e.g. we can swim)

• obligative: must do (e.g. whales must swim)

define adaptability

the degree to which a species can survive and reproduce in different environments

name features of behavioral flexibility

optimality, non-conscious decision making, formal models, proximate currencies (e.g. calories) easier to quantify than fitness, niche

whats optimality

costs & benefits of different strategies

outline not-conscious-decision making

e.g. sex didn’t evolve because it makes us think of babies

outline proximate currencies

e.g. calories are easier to quantify than fitness, different currencies can be optimized e.g. search time, predation risk

what is n evolutionary niche?

environmental way of life for an organism, greater overlap leads to greater competition (e.g. prey size) - e.g. foxes and wolves tend to cohabit well as they have different prey sizes, but cyotes struggle

outline an example of a ecological niche in humans

sickle cell anemia is heterozygotes is associated with malaria resistance, so more individuals with SCA in malaria areas

what is the ‘carpentered’ niche

perception of the muller-lyer illusion is generally attributed to straight lines in urban environments, doesn’t work on tribes with no corners

critiques of behavioral ecology

focusses on adaptive behavior (current function) and not on adaptions (history)

• behaviour not psychology

• ignores constraints on adaptiveness - e.g. that natural selection will always favour traits with high fitness

what are the 2 levels of explanation of behaviour? (Mayr’s levels)

• ultimate causation - refers to evolutionary levels of explanation

• proximate causation - refers to immediate circumstances

what are Tinbergen’s 4 questions?

• Ultimate (why) questions

  • function; adaptation, fitness value of a trait (reverse engineering)

  • evolution; phylogeny, evolutionary history of a trait

• Proximate (how) questions

  • Development; ontogeny, traits variation throughout development, recapitulates phylogeny

  • Causation; (mechanism) immediate circumstances affecting a trait e.g. stimuli that elicit a response, neurology, hormones