Human evolutionary history Humans show similarities with ‘apes’ (gibbons, orang, gorilla, chimps) shared derived traits: large brain, no tail, more upright posture other Old World monkeys ‘apes’ and humans increased brain size loss of tail upright posture

Human evolutionary history Which are closer: gorilla & chimps or humans & chimps? are traits shared derived versus convergent / lost? human similarities in teeth, skull, genitals gorilla ? chimps human knucklewalking morphology gorillachimps

Human evolutionary history Molecular data suggests chimps and human are close relatives human similarities in teeth, skull, genitals gorilla  chimps human knucklewalking morphology gorillachimps DNA similarities common ancestor ~5 million yrs ago

Human evolutionary history Humans’ closest living relatives are chimpanzees shared derived traits: morphological: skull, teeth, genitals behavioral: hunting, tool use, social behaviors other Old World monkeys chimps increased brain size loss of tail upright posture gibbons skull elongation loss of some hair brow ridge orang gorillahuman similarities in teeth, skull, genitals many unique traits

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Figure 19.3 Millions of years ago Australopithecus anamensis Ardipithecus ramidus Ardipithecus ramidus kadabba Orrorin tugenesis Australopithecus afarensis Australopithecus africanus Australopithecus robustus Australopithecus boisei Homo ergaster Homo habilis Homo erectus Homo neanderthalensis Homo sapiens ?

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings The earliest hominids were a diverse group –Various species of Australopithecus date from about 4 to 1 million years ago –Our own species, Homo sapiens, is the only hominid that has not become extinct

Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings Australopithecines had relatively small brains –This indicates that bipedalism preceded the evolution of the enlarged brain –Bipedalism is a basic human trait 19.4 Upright posture evolved well before our enlarged brain Figure 19.4

A brief history of human brains  Neandertals - large brains 200,000 years ago  Modern homo sapiens (and their brains) evolved ~ 100,000 years ago in africa  Most toolmaking came tens of thousands of years later  Agriculture and the rapid growth of human populations came 90,000 years later

Evolution

Evolution of mind  The mind evolved just like the rest of the body. The principle is clear, but the details are highly contentious  What might have been a driving force for human minds?  The mind evolved just like the rest of the body. The principle is clear, but the details are highly contentious  What might have been a driving force for human minds?

Evolution

The Mating Mind Geoffrey Miller Why do we have big brains?

Evolution of the brain Evolution of the brain  Brain is expensive brain energy use as a percent of resting body usage most vertebrates: 2 to 8% apes and some monkeys: 13% Humans: 20%  Evolution requires you to pay your way as you go; no investment for 50,000 years in the future  What was the brain used for in the mean time?

Forms of Darwinian Selection  Natural selection "nature red in tooth and claw" competition for food and for staying alive  Sexual selection Competition for mates

Sexual Selection  Female mate selection asymmetry of costs lead to male display and female selection male birds generally have the plumage male humans have orgasm relatively easily, females less easily Females are choosing  but also male selection in humans - why? hidden estrous requires multiple copulations male investment in childrearing?? or just ongoing courtship

The Handicap Principle  Handicap’s provide useful signalsthat the male is fit Handicaps in human  Aside: the immorality of handcap  Sexual selection causes runaway "fads" peacock's feathers

Advertising fitness  Fitness Genetic quality Health and nutrition  Sports what do you win? - status  Conspicuous consumption  Conspicuous generosity not kinship or reciprocal altruism

Theory of mind