Summary of Climate and Evolution

Key Concepts of Evolution Relevant to Climate Effects

· Evolution from isolated populations
(Example: Galapagos finches, differing human cultures in Polynesia)

· Environmental circumstances create “selection” pressures
(Example: Periods of cooling in N. Europe)

· Severe reductions in size of a population create “bottleneck”
effect, possibly leading to rapid evolutionary changes
(Hypothesized example: Huge volcano event ~70,000 BP)

“Turnover Pulse” Hypothesis

· During stability, specialists of populations fill marginal niches

· Ecosystems undergo periodic disruption

· Disruptions result in extinctions (especially of specialists)

· Extinctions create new opportunities leading to opportunistic speciation

· Stability reestablished

Theory on Human Evolution in Africa’s Rift Valley

· Roughly 5 to 6 million years ago, split in earth’s crust isolated
two subpopulations of Ardipithicus in East African valley

· Environment of one population remained relatively stable (rainforest)

· Increased aridity (possibly rain shadow effect) led to savannah habitat
for second population

· Savannah population evolved into Australopithecus, ancestor of
Homo sapiens