Transcript PPT
Check revised lecture notes! Time Line • 1.8 MYBP Beginning of Pleistocene • 1.7 MYBP Ancestral mammoth arrives in America • ~ 0.2 MYBP Modern humans evolve in Africa • ~ 0.015 MYBP Modern humans arrive in America • 0.01 MYBP 135 spp. extinct, last glacial retreat Dispersal of Humans Nature 7 Dec. 2000 p. 653. Climate Change in Pleistocene Humans arrive in Australia Humans arrive in America Australia • Colonized ~ 50,000 years ago. • No global warming at this time. • Offers a natural experiment to compare human predation and climate change. Genyornis Gifford Miller, 1999 Genyornis (1999 Research!) Miller et al., 1999. Science 283: 205-208 Summary (but 8 years ago!) • “From consideration of all of these stories for different continents there does not appear to any one factor responsible for the late Pleistocene extinctions . . . What is likely is that the primary lethal effect was the combination of these factors, acting in a synergistic manner on a fauna unaccustomed to so many disruptions at once.” Burney 1993. My Opinion • Human Hunting – Almost certainly – More work needed on early social structure • Humans as Disease Vectors – Intriguing • Predator-Prey Theory – Not an issue in America or Australia – Relevant to Africa • Climate Change – Probably a factor in America Are we on the verge of a MASS EXTINCTION? Review: Deterministic Threats • Change in physical environment – climate change – habitat destruction – pollution • Change in biotic environment – Competition – Predation (including disease and human hunting) – Mutualism Current Extinction Methods of Humans • Overkill (Stellar’s sea cow) • Introduced species – predators, disease, competitors • Habitat destruction • Global climate change • Warfare The Last Stellar’s Sea Cow, 1768 Whales Hunted to Near Extinction • 1800’s - A record three year cruise killed < 100 whales. • 1933 - ~30,000 whales killed, 2.5 million barrels of whale oil. • 1967 - ~60,000 whales killed, 1.5 million barrels of oil Introduced Predators Domestic animals become feral predators Brown tree snake (Guam rail) Tibbles eats all Stephan Island Wrens (1894) W.B. Espeut introduces mongooses onto Jamaica (1872) Bird Extinctions in Eastern N.A. The Heath Hen: Multiple Causes Nature Conservancy magazine July/August 1998 p. 8-9 Disease New Scientist 5 August 2000 p.35. Article by Debora MacKenzie Humans and Disease http://www.sciencemag.org/cgi/content/full/287/5452/443 Lyme Disease Deforestation • 110,000 km2 per year, 20 hectares per minute (A. Sommer, 1976) • 55 km2 per year (an area the size of WV), 10 hectares per minute (P. and A. Ehrlich • 150,000 km2 per year, 25 hectares per minute, one football field every second (N. Myers 1989). Deforestation