Symbiosis

Humans live in symbioses of various intensities with a number of domesticated animals and plants. To varying degrees, these cultural symbioses are mutualistic, with both humans and the other species benefitting.

For example, all important agricultural plants exist in tight mutualisms with humans. Agricultural varieties of corn or maize (Zea mays), for example, are no longer capable of reproducing independently of human management. This is because over time the fruiting structure of maize has been selected to be enclosed in a leafy sheath that does not open, and to have seeds that do not easily separate (or shatter) from the supporting tissue (the cob). If humans did not plant the seeds of maize, the species would rapidly become extinct, because it no longer occurs as wild populations. The same is substantially true for most agricultural plants that have become extensively modified through cultural selection by humans. Humans, of course, benefit greatly from their mutualisms with agricultural plants, through the provision of crops of food, fiber, and other products.

Similarly, agricultural animals live in a symbiotic mutualism with humans. Cows (Bos taurus), for example, benefit from their human-managed access to fodder, veterinary services, and protection from predators, while humans benefit from access to milk and meat.

Even the keeping of animals as pets represents a type of mutualism. Pet dogs (Canis familiaris) and cats (Felis catus) are fed and kept safe in domestication, while humans benefit from the companionship of these animals, and sometimes from other services, as when cats kill pest rodents.