One of the most important conditions of for civilisation is economic. Agriculture is the key to civilisation: without it, a society would base its economy on hunting and gathering. This would only allow temporary settlements. Agriculture not only forces a group of people to settle (plot of land cannot be moved), but also provides a food supply much larger and reliable than the hunting gathering economy. A reliable supply of water and food teaches mankind to work with order and regularity and to plan in the long term. It also requires less people directly involved in the food supply activities, thus allowing a portion of society to be relatively free from labour and to engage in other activities. Previously, among nomads, one roving band met another and there was a display of force in order to gain the right to exploit a specific area. These encounters were usually not deadly if other areas still unexplored. The weaker band, foreseeing a defeat, would retreat and search for another area. There was no area worth the loss of life. Farmers, on the hand, did not really have a choice, they had to defend their immovable farms. To stand and fight was their only alternative. By defending their farms they had chance to survive, their only other option was to die of starvation. This was the beginning of organized warfare. Another condition for civilisation is intellectual: many aspects could be included here, such as language unity, and the pursuit of knowledge (philosophy, science, art). There has to be some language unity to allow the exchanging of ideas. This could be either a homogeneous fully consistent language or a variety of dialects close enough to prevent language barriers. Mental exchange feeds into the developing of philosophy, science and arts, enriching the cultural development and facilitates the transmission of morals and education. This might sound like an extremely basic point but it is often taken for granted. However, a language complex which is homogenous enough to allow these consequences seems to be a relatively later achievement in human history.