The idea that Gaia is an "organism" is oversimplified, however. It would be more accurate to say that Gaia is a complex adaptive system--that is, it belongs to a larger category of teleogenic systemic phenomena of which ecosystems, organisms, and cells are other instances--some loosely, some more tightly coupled--at lower holarchic levels. The biologist Tyler Volk, a prominent Gaian scientist, put it this way: "cells are cells; organisms are organisms; and Gaia is Gaia." And the idea of nature as "a violent place" is also an oversimplification of Darwin's thinking, for nature includes multiple interacting relationships: not only competition and predation, but also mutual avoidance (niche-defining), commensalism, symbiosis. And we humans, too, share these characteristics with the rest of nature.