EVOLUTIONARY BASES OF BEHAVIOR

DARWIN’S INSIGHTS Wrote On the Origin of

Species Identified natural

selection as the mechanism that controls the process of evolution

Attempted to discover why organisms developed traits that suited them for their environment

DARWIN Noticed animals vary Noted some

characteristics are heritable

Noted organisms reproduce at a pace that outdoes food supply and other resources

Therefore: traits that increase reproduction increase an organisms’ survivability

EVOLUTIONARY THEORY “Survival of the fittest” Fitness: reproductive

success of an individual organism relative to the avg reproductive success in the population

2 ways traits contribute to evolution:

1: survival advantage 2: reproductive

advantage

NATURAL SELECTION Def: heritable

characteristics that provide a survival or reproductive advantage are more likely than alternative characteristics to be passed on to subsequent generations and thus they come to be “selected” over time

CONTROVERSY Went against idea of

divine intervention in life

Implied humans are not unique and they share a common ancestry with other species

REFINEMENTS Theodore

Dobzhansky synthesized Darwin’s theories with the genetics work of Gregor Mendel

Contemporary: gene pool shaped by genetic drift, mutations, and gene flow

ADAPTATIONS Def: inherited

characteristic that increased in a population b/c it helped solve a problem of survival or reproduction during the time it emerged

Key product of evolution

INCLUSIVE FITNESS Def: the sum of an

individual’s own reproductive success plus the effects the organism has on the reproductive success of related others

Explains paradox of self-sacrifice

BEHAVIOR AS ADAPTIVE TRAITS Patterns of behavior

reflect evolutionary solutions to adaptive problems

Camouflaging, fleeing, selective reproduction

PARENTAL INVESTMENT AND MATING SYSTEMS

Parental investment: what each sex has to invest—time, energy, survival risk—to produce and nurture offspring

Most males contribute little, females contribute the most

POLYGYNY When investment is

high for females and low for males:

Polygyny: mating system in which each male seeks to mate w/ multiple females, whereas the female mates w/ only one male

Favors aggressively competitive males

POLYANDRY Def: mating system

in which each female seeks to mate with multiple males, whereas each male mates w/ only one female

Very rare

MONOGAMY Def: mating system

in which one male and one female mate exclusively (or almost) with each other

MISCONCEPTIONS ABOUT EVOLUTION 1: Evolution is only a theory---evidence to

support is substantial 2: Evolutionary analyses assume that

organisms have a motive to max reproductive fitness

3: Evolutionary analyses embrace genetic determinism