1. Check updated study questions and help file on calculating background rates of extinction. Exam Resources Section

2. Cenozoic Era Epoch Holocene (Recent) Pleistocene Paleocene.01 1.8 5 24 37 58 65 Million years ago Paleogene Neogene New period names Cretaceous Eocene Oligocene Miocene Pliocene Quaternary Tertiary Traditional period names

4. American Pleistocene Extinctions 135 species of large mammals went extinct in N. and S. America about 11,000 years ago. Why? –Climate change –Human mediated

5. http://www.sciam.com/2000/0900issue/0900nemecekbox2.html Early Sites in the Americas Clovis People expand into the Americas 15,000 years ago Maybe 20-40,000 years ago

6. Clovis People’s spear and arrow points, scrapers

7. Human Predation Overkill Hypothesis –Archeological evidence of hunting tools –Arrow points etc. embedded in fossilized bones Blitzkrieg –Naïve predators or ineffective defenses

8. New World Blitzkrieg?

9. But... Predator-Prey Theory? Prey Density Time Predator switches to more common prey Prey is maintained at low density

10. Mammoth Hunter... or Fish Catcher? http://www.sciam.com/2000/0900issue/0900nemecek.html

11. Human-Mediated Extinction Predation –Overkill –Blitzkrieg Disease Fire

12. Human Rats http://www.sciam.com/interview/2001/010201macphee/index.html

13. Gradual Extinctions?

14. Climate-Change Hypothesis ME took place during the last glacial retreat 10 to 11,000 years ago. Less savanna and grasslands, and more deciduous forests and swamp environments. Hypothesis: Mega-herbivores went extinct and destabilized communities. The whole pyramid tumbled.

15. Evidence Against No large-scale extinctions of mega- vertebrates for previous glacial retreats. More extinctions expected in areas most affected by climate change –north of N.A. and tropics of S.A

16. Interaction of Hunting and Climate Change Mega-herbivores as “ecosystem engineers” –Keystone Herbivore Hypothesis Domino Extinctions

17. Keystone Owen-Smith: Keystone Herbivore Hypothesis (1987) Removal of keystone herbivores causes extinction cascade for midsize herbivores and their predators (Domino Effect)

18. The Chicken and the Egg

19. Large mammals selected against: Taxa of South American land mammals Existing before man’s arrival Genera:1535654 Extinct 10,000 years ago Large-bodied species 96% Large and small species

20. Pleistocene Survivors - I Holarctic Distribution –grizzly bear, moose, elk, wolves, musk-oxen But... –llama, tapirs, prong-horn antelope, mountain goat

21. Pleistocene Survivors - II Susceptibility to environmental change –Grizzly bears vs. sabre-toothed tigers Vulnerability to human hunters –Mountain goat vs. woolly mammoth

22. % Extinctions of Terrestrial Genera ( >44 kg adult) ExtinctLivingTotal% Extinct Africa7424919.3 N. A.33124573.7 S. A.45125778.9 Australia1932286.4

23. What About Africa? Human history? Climate change? Equivocal evidence