Human evolutionary history

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

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

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

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

5. ? Australopithecusrobustus Homoergaster Australopithecusafricanus Homosapiens Australopithecusafarensis Homoneanderthalensis Millions of years ago Homoerectus Australopithecusanamensis Homohabilis Australopithecusboisei Ardipithecusramidus Ardipithecusramidus kadabba Orrorin tugenesis Figure 19.3

6. 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 • The earliest hominids were a diverse group

7. 19.4 Upright posture evolved well before our enlarged brain • Australopithecines had relatively small brains • This indicates that bipedalism preceded the evolution of the enlarged brain • Bipedalism is a basic human trait Figure 19.4

8. 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

9. Evolution

10. 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?

11. Evolution

12. Evolution The Mating MindGeoffrey Miller Why do we have big brains?

13. 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?

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

15. 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

16. 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

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

18. Theory of mind