"Symbiosis is an ecological phenomenon where one kind of organism lives in physical contact with another. Long-term symbiosis leads to new intracellular structures, new organs and organ systems, and new species as one being incorporates another being that is already good at something else. This major mode of evolutionary innovation has been ignored by the so-called evolutionary biologists. They think they own evolution, but they’re basically anthropocentric zoologists. They’re playing the game while missing four out of five of the cards. The five are bacteria, protoctists, fungi, animals, and plants, and they’re playing with just animals—a fifth of the deck. The evolutionary biologists believe the evolutionary pattern is a tree. It’s not. The evolutionary pattern is a web—the branches fuse, like when algae and slugs come together and stay together."

Lynn Margulis