Evolution: Basic Principles Evolution: Change over time; decent with modification Natural Selection: Primary mechanism producing evolution (change over time). There are other mechanisms such as: sexual selection, social selection, drift. Basic principles of NS: Variability: stuff varies Heritability: variation is passed on genetically Competition: limited resources Selection: some variations are advantageous in securing limited resources and tend to passed on more than others = change over time Spencer’s misleading summary of NS: “survival of the fittest.”

Terms and concepts Mutation: copying error in genetic transmission. Provides the variability upon which selection can operate. Most mutations are neutral or detrimental, but occasionally a beneficial. Are mutations entirely random? Fitness: Differential reproductive success Future Blindness: Creatures are adapted to past conditions. The best bet on what the future is going to be like is the past. But that may not always be true. Chance and law: chance – the future; mutations. Law – traits that increase fitness will get passed along, those that detrimental to fitness will be selected out. Preadaptation: NS can only work with what it is given, traits and structures “designed” originally for one purpose must be re-fashioned for later ones. This places limits on future adaptability. Critical question: does a creature have traits whose preadaptations allow it to be re-molded to met current challenges? If so, it might survive, it not, it may go extinct. Ex: Humans has pre-adaptations that allowed for bi-pedalism, large brains, symbolic functioning, not for flying.

Other key concepts Modern Synthesis: (neo-Darwinism) combo of Darwinian selection with Mendelian genetics. Adaptations: inherited, phenotypic solutions to adaptive problems Byproducts: non-adaptive incidental tag-alongs to adaptive traits. Navel is byproduct of adaptation of umbilical connection of mammalian mother to offspring. Noise: Random non-adaptive characteristics of adaptations or byproducts. Inny vs. outie navel; dry hair, frizzy hair etc. Exaptation: (closely connected to pre-adaptation) adaptive trait or structure whose original function was different what it currently performs (human inner-ear bones originally jaw bones of reptiles)

Sexual selection Some traits may actually be detrimental to survival but provide an advantage in mating.

Sexual selection: intra-sexual competition Typically male-male competition for mates, resources, and status.

Evolutionary basis for male competition Gamete size: ultimate determinant of “malesness” and “femaleness.” Leads to differences in parental investment. (cheap sperm vs. expensive eggs) Parental investment : any investment in current offspring that precludes investment I future offspring. (mating vs. parenting effort) Parental certainty: extent to which on can be assured that offspring carry one’s genes. (paternal vs. maternal certainty); high for females, low for males

Intra-sexual coalitional competition Chimpanzees are especially well-known for forming male coalitions to challenge other males for dominance.

More concepts Domain specificity: A psychological adaptation is specific to an adaptive problem, does not apply generally to a range of potential problems. Ex: cheater detection mechanism. Controversy as to how widespread this type of design is. EEA: Environment of Evolutionary Adaptiveness. The original selection pressures which shaped the present adaptation. Inclusive fitness: W.D. Hamilton – fitness should include not just direct offspring but kin offspring as well; gene’s eye view of evolution Connection to sociobiology: EP – greater emphasis on psychological mechanisms and less on current adaptive significance. Humans as “adaption executers, not fitness maximizers.” Key concept: NS cannot make you have alot of offspring, it can only motivate you to engage in those behaviors that in the past were associated with higher rates of reproduction.

Social Selection Some traits help animals get along better in their social groups which in turn increases their survival and reproduction. Ex: more socially skilled female baboons tend to have more surviving offspring.

Traits: Evolutionary origins Homologous traits: shared by a species because of common ancestry (ex: high EQ; sociality; tool use, present in humans and other apes inherited from common ancestor, “ancestral” traits). Analogous traits: traits shared because of similar selection pressures (“camera” eye design in human and octopi). Evidence for convergent evolution. Derived traits: traits unique to a species because of particular selection pressure faced during its evolutionary history (hairlessness, habitual bipedalism, tool dependency, in humans).