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 arrivein Australia

Humans arrivein America

Australia

• Colonized ~ 50,000 years ago.

• No global warming at this time.

• Offers a natural experiment to compare human predation and climate change.

Gifford Miller, 1999

Genyornis

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

Brown tree snake(Guam rail)

Tibbles eats allStephan Island Wrens (1894)

W.B. Espeut introducesmongooses onto Jamaica (1872)

Domestic animalsbecome feral predators

Introduced Predators

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