The Principle of Maximum Diversity

And then life will diversify to fill the infinite variety of ecological niches in the universe, as it has done already on this planet. If you want an intellectual principle to give this picture a philosophical name, you can call it “The Principle of Maximum Diversity”. The principle of maximum diversity says that life evolves to make the universe as interesting as possible.  A rain-forest contains a huge number of diverse species because specialization is cost-effective

- Freeman Dyson