During the Jurassic period gymnosperm plants (pine trees) were pollinated by flying insects. Nowadays they are generally pollinated by wind. Some time later during the Permian period angiosperms began to be pollinated by insects; first by beetles, then by flying insects and eventually bees. Since angiosperms did not evolve form gymnosperms and beetles did not evolve form insects. pollination symbiosis must have developed independently twice.
—David Foss