The idea of a trade-off goes back to the ancient Greeks,when Heraclitus pointed out that it was the basis of defining a problem.Hegel called it the dialectic,Engels used the idea to model evolution and Marx applied it to economics.At some point Pareto pointed out that it was something to do with optimisation,and Genrich Altshuller used the same notion in his formulation of TRIZ(Theory of Solving Problems Inventively).The Pareto set is being introduced into ecological theory to model adaptive evolution and(almost)to define "ecological niches" as a series of mutually exclusive trade-offs,which can co-exist in any number.