Orc
The orc race survives in a vicious cycle of Malthusian principles. While their population continues to grow exponentially, their territory, food, and other resources can only appreciate linearly (if they increase at all). Huge breeding numbers, fast maturation time, and a massive gender disparity cause the orcs to forcibly kick out their adolescent (but still battle-ready) males at age eleven. This rite of passage involves surviving outside orc territory for a period of five years before being allowed re-entry. During this time, the older orcs still within the established settlement will actively treat the castaways as enemies, providing incentive for them to get as far away from orc-held territory as possible. Many of those forced out band together to form the crux of the common outsiders' experience of the orc race: raiding parties. Threatening enough to harass the fringes of society (and generally be a nuisance) but not enough to break a legitimate defense, for most eons the orcs remain scattered and direction-less.
Additional Information
Perception and Sensory Capabilities
Darkvision: An orc can see in the dark up to 120 feet. Darkvision is black and white only, but it is otherwise like normal sight, and an orc can function just fine with no light at all.
Genetic Descendants