California State University Long Beach 

Climate change and humankind

• Biological evolution
• Extinctions and evolutionary radiation
• Associated with:
• Climatic change
• Catastrophic events
• Tectonic opening/closing of land bridges
• Human evolution in Africa
• Fragmental, discontinuous sedimentary record on land
• Human fossils, artifacts, & pollen records
• Excellent marine records in Arabian Sea and Indian Ocean
• Oxygen isotopes and wind-blown dust records

Climatic & evolutionary steps in human evolution

• 2.5 Ma
• First fossils of genus Homo
• First step of aridification of northeastern Africa
• Associated with growth of Northern Hemisphere glaciation
• 1.7 Ma
• First Homo erectus fossils
• Second step of African drying
• ~1.0 -0.8 Ma
• Migration of Homo erectus from Africa
• Final drying step
• Start of 100,000 year glacial cycles
• Complete conversion of forests to grasslands

Implications

• Climatic and environmental stress effects evolution
• Increased competition (harsher environment):
• Stimulated growth of larger brains
• Stimulated better tool using abilities

Human migration

• Homo sapiens (our species) evolved during glacial/interglacial oscillations
• Habitable regions limited by climate
• Tundra, ice sheets, deserts were too harsh
• Access to habitable areas restricted by climate
• Sea level, glaciers, deserts block travel
• Migration from Asia to North America
• Approximately 12,000 years ago
• Paleoindians crossed the Bering Land Bridge
• After ice sheets had retreated
• Before being drowned by rising sea level
• Thousand-mile-wide exposed continental shelf between Siberia and Alaska
• Indicated by:
• Age of campsites, tools, and slain animals
• Northeastern Asia (Kamchatka)
• 14,300 to 13,400 years ago
• Alaskan North Slope camps
• 11,700-9,700 years ago
• Clovis, Folsom sites, New Mexico
• 11.200-10,900 years ago
• Peat deposits from moist tundra vegetation distributed across the present Bering Sea
• As young as 11,000 years old

• Mastodons, mammoths, giant beavers, saber tooth cats
• Human hunting or climatic/environmental change?

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