Did Climate Deterioration Play Major Roles in Human Evolution?

1. Did Climate Deterioration Play Major Roles in Human Evolution? With thanks to Robert Boyd and Robert Bettinger http://www.des.ucdavis.edu/Faculty/richerson/richerson.htm CEFOM Symposium Cultural and Ecological Foundations of the Mind Hokkaido University, June 25, 2003

2. OUTLINE Climate Deterioration on Several Time Scales Brain Size Increase Origins of Human Culture Progressive Trends in Human Evolution Origins of Agriculture Current Climate Change

3. Macroevolutionary Explanations Internal to evolutionary processes External, caused by environmental change

4. CLIMATE DETERIORATION

5. Stable Isotope Fractionation 18 Oxygen water versus 16 Oxygen water

6. Cenozoic Climate Cooling and Drying From Kennet 1995

7. Climate Deterioration Since the Miocene From Neil Opdyke, 1995

8. Early Hints of Millennial Scale Variation From H.H. Lamb, 1977

9. Ice Drill Rig on Greenland From Richard Alley, 2000

10. Greenland Core locations From Richard Alley, 2000

11. GRIP Greenland Ice Core Resolution of millennial and sub-millennial scale variation After Peter Ditlevsen, 1993

12. Abrupt Change From Severinghaus and Brook, 1999

13. But Ice Caps Are Not Human Environments

14. Santa Barbara Basin Winter and Summer Temperature From Hendy and Kennett, 2000

15. Arabian Sea Total Organic Carbon From Schultz, von Rad, and Erlenkeuser, 1998

16. Tropical Atlantic Color From Petersen et al., 2000

17. Southern Italian Pollen From Allen and Hundley, 2000

18. Santa Barbara Pinus Events From Heusser and Sirocko, 1999

19. Causes of Climate Deterioration

20. Rise of Tibetan Plateau increases albedo Drake Passage opens, Circum-Antarctic Currents insulate Antarctica Seafloor Spreading and Climate Deterioration

21. Warm Earth Cool Earth Cold Earth Broecker's Thermohaline Conveyor Hypothesis

22. Meltwater Discharge Streams Change With Ice Cap Size Clark et al., 2001

23. Did Climate Deterioration Favor Larger Brains?

24. Cenozoic Climate Cooling and Drying From Kennet 1995

25. Mammalian Brain Size Increase From Jerison, 1973

26. What Time Scales of Variation Drive Brain Evolution? Richard Potts "Variabilitly Selection" Hypothesis Versus Millennial and Submillenial Scale Variation

27. Orbital Scale Variation 22 kyr axial wobble dominates 41 kyr axial tilt dominates 100 kyr orbital eccentricity dominates

28. If environmental change slow, genes keep up What Is Culture Good For? A contest between systems: Genes plus learning Genes plus individual learning plus culture If environmental change is large and If environmental change is not too fast or too slow, Then culture is a big advantage If environmental change too fast, culture useless If not much environmental variation, culture not much use 1 = trust mom completely, 0 = trust own experience completely

29. GRIP Greenland Ice Core After Peter Ditlevsen, 1993

30. Hypotheses: What if millennial and submillennial scale variation is tied to amplitude of the orbital scale variation? Variance Cascade Hypothesis What if brain size is a rough indicator of millennial and submillennial scale climate variation? Bioindicator Hypothesis

31. Orbital Scale Variation 22 kyr axial wobble dominates 41 kyr axial tilt dominates 100 kyr orbital eccentricity dominates

32. Mammalian Brain Size Increase From Jerison, 1973

33. Stone Tool Traditions From Richard Klein, 1999 Oldowan 2.5-1.7 Myr BP Acheulean 1.65-0.250 Myr BP Mousterian 0.250-0.044 Myr BP Aurignacian 0.040-0.028 Myr BP

34. Australopithecines 41 kyr dominance starts Early Homo Early Hominid History From Richard Klein, 1999

35. Last glacial begins 100 kyr dominance begins The Genus Homo From Richard Klein, 1999

36. Was Agriculture Impossible Under Last Glacial Conditions?

37. Anatomically Modern Humans First Agriculture Out of Africa II

38. Dates for Origins of Intensive Foraging and Agriculture

39. First Agriculture Late Natufian Natufian Younger Dryas Cold Episode and Levantine Cultures From Grafenstein et al., 1999; Goring-Morris and Belfer-Cohen, 1998

40. The Little Ice Age From Dust Jacket Book by Brian Fagan, 2000 The Cencus at Bethlehem Peiter Brueghel the Elder, ca 1650

41. Now: Global Warming All OK? Worry: Complex, Poorly Understood Feedbacks

43. Barrett Nature 2003

44. Arctic Ocean Ice Thinning Reduced deep water outflow thru Denmark Strait Broecker's Thermohaline Circulation Hypothesis

45. 2002 Report of the National Academy of Sciences’ Committee on Abrupt Climate Change Chaired by Richard B. Alley “Available evidence suggests that abrupt climate change is not only possible but likely, potentially with large impacts on ecosystems and societies.” “We do not yet understand abrupt climate changes well enough to predict them.” “Societies and ecosystems have an easier time dealing with slower or better anticipated changes, so the abruptness and unpredictability of the possible changes may be disquieting.”

47. CONCLUSIONS New climate data permits much better external hypotheses These hypotheses will be tested Anthropogenic climate change worth worrying about

48. Cultural differences in psychological functioning • Adaptation to diverse environments in time and space • Cultural pseudo-speciation • Institutions and cultural differences • Social organizational adaptations diverse • Non-adaptive diversity via design complexity (folk theorem, games of coordination) • Methods of analysis • Field studies of microevolution • Laboratory studies of microevolution