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Quick climate fluctuations invoke tolerance adapta-tion: being able to survive in a wider variety of habitats and climates. For hominids, behavioral facets of adaptive tolerance included flexibility in diet, tool use, and clothing.
As hominids lived in groups under taxing environmen-tal conditions, the demands of sociality also drove mental development. As with phenotype, a combination of prob-lem-solving and social pressures fomented mentotypic evolution.