QUATERNARY FAUNAS

Rancholabrean: Los Angeles, CA
Irvingtonian: San Francisco Bay area

1. Superposition: younger overlies older
   Steno
   
   
2. Stage of Evolution: long-term trends in morphologic change
   
   
   
   
3. Dispersal: land bridges
   
   

NORTH AMERICAN LAND MAMMAL AGES
Characterizing Assemblages

THE MEGAFAUNAL EXTINCTIONS

Megafauna vs. Microfauna

Extinction Chronology

Global Timing of Megafaunal Extinction

Paul Martin's Overkill Hypothesis

• Extinctions earlier in north than in south, human shock-wave "blitzkreig"
  
• Annual travel less than 20 km
  
• Extinction event brief, killing event, so sites rare
  
• Climatic change too gradual
• Climatic change at wrong time to cause faunal extinction (cf. Haynes, 1991)
• Earlier deglaciations did not cause extinction

Monte Alegre

Monte Verde

Historic Extinctions

• Oceanic Islands Holocene Extinction
  • Ground Sloths, West Indies, 4400 C¹⁴ yr BP (Steadman et al., 2005)
  • Pigmy Mammoths, Wrengel Island, 3730 C¹⁴ yr BP (Vartanyan et al., 1995)
    no evidence of human presence
  • Birds Pacific Islands, 2850 C¹⁴ yr BP (Steadman et al., 2002)
  • Megafauna Madagascar, 1720 C¹⁴ yr BP (Burney et al., 2003)
          gorilla-sized lemur
  • Birds New Zealand, 600 C¹⁴ yr BP (Holdaway and Jacomb, 2000)
  
  
  
• Australian & Japanese Megafauna Extinction 30 - 60 Ka
  does it coincided with arrival of humans?
  
  

  MARINE OVERKILL: SERIAL EXTINCTION

  MARINE OVERKILL (background: great whale harvest) "We propose that decimation of the great whales by post- World War II industrial whaling caused the great whales’ foremost natural predators, killer whales, to begin feeding more intensively on the smaller marine mammals, thus"fishing-down" this element of the marine food web. The timing of these events, information on the abundance, diet, and foraging behavior of both predators and prey, and feasibility analyses based on demographic and energetic modeling are all consistent with this hypothesis."