Although competition for vital resources is indeed a part of every life-bearing environment, and the winnowing of competitors through natural selection is essential to the evolutionary process, cooperative symbiotic arrangements are not only essential, but appear to have been necessary for driving evolution at the pace it has unfolded on earth. The discovery that the energy-producing engines of plant and animal cells probably resulted from the union of formerly separate organisms places symbiosis at the center of life's origins, evolution, and continuation.

Nitrogen, for example, is a resource necessary for the growth of plant life, yet plants are not capable of producing it efficiently and independently, but plant life does not consist solely of those victorious competitors who manage to sequester sufficient supplies of this resource. The roots of many species of trees host fungi that in turn create hospitable environments for bacteria that are capable of fixing nitrogen in the soil in a form useful to the trees. The trees, fungi, and bacteria create environmental conditions, through their specialized capacities, that encourage one another's growth; instead of competing for a scarce resource, these different kinds of organisms work together to produce it in abundance. Similarly, every human carries twenty times as many living bacteria as human cells - 90% of the dry weight of human feces consists of the bodies of intestinal microbes. Humans and other animals are able to digest a wide variety of substances solely because we have evolved myriad symbiotic partnerships with a wide variety of microorganisms.

The capacity of different microorganisms to exchange and combine genetic material, from the useful emergence of mitochondria and chloroplast-bearing cells to the dangerous (to humans) endosymbiotic union of different animal forms of influenza strains, constitutes a vast and rapid engine for genetic change. Nobel winning evolutionary biologist Joshua Lederberg remarked in a 2002 lecture: "Together with its symbionts/parasites, we should think of each host as a superorganism with the respective genomes yoked into a chimera of sorts."
The way in which early life forms may have altered the chemical composition of the atmosphere, ocean, and earth's crust led James Lovelock to propose the Gaia Hypothesis - that life on earth is a vast and complex, self-regulating, superorganism, in which the separate parts cooperate in order to maintain an environment supportive of their existence and evolution.