Trait Plasticity:

David C. Geary:

"Trait plasticity can evolve if some features of the ecology or social environment that drove the evolution of the trait fluctuate during lifetimes. If the ability to adapt to these fluctuations influences survival or reproductive prospects, then conditions are set for the evolution of trait plasticity. The conditions that create such fluctuations can be climatic or result from biological arms races. The latter are common among organisms with competing interests, as in predator-prey and host-parasite relationships (Darwin, 1859; Dawkins & Krebs, 1979). They are also common in species that live in complex social groups, which results in ever changing patterns of cooperation and competition for control of resources associated with survival or reproductive prospects."