Three statements can summarize the state of affairs of both the simplest bacterium and the most self-assured twentieth century human being. In order to maintain access to resources, organisms sometimes interfere with their neighbors. Without resources, organisms will die, and so the contest to find, harvest, transport, store and retain possession of resources is part of the struggle for survival. Long before scientists such as Darwin concerned themselves with formal scientific study of competition, there was an intuitive appreciation of its importance, both in the realms of politics and agriculture. In his campaigns in Gaul, Caesar describes the siege of Uxellodonum in 51 B.C., where he not only surrounds the town by earthworks, but builds a second ring of trenches with pitfalls and sharpened stakes facing outwards to prevent any attempts at rescue by neighboring Gauls.
Roman soldiers deny access to the local river.
The townsmen however still resisted obstinately and held out even when numbers had died of thirst, until in the end our mines tapped the rivulets which supplied the spring and diverted them. More than a century ago, Malthus and Darwin both understood that the intrinsic nature of organisms to multiply exponentially against limits set by resources produced a struggle for survival. The capacity for exponential growth means that both houseflies and elephants, given sufficient time, could multiply rapidly enough to entirely cover the land areas of Earth. Both Malthus and Darwin realized that the reason that this did not happen was that some other factor, usually a shortage of resources, prevented most young from surviving. Although each elm tree in a forest may produce millions of seeds, only one need reach adulthood for each tree to be replaced and the forest to remain intact.