Why did populations concentrate in smaller areas during the agricultural?

many reasons. As agriculture developed one human or a small group of humans could produce enough dough to supply themselves and many others relatively easily. This allowed those other people to focus on other more specialized tasks, because they could get food by trading goods or services directly or later for currency. These people who where not growing food began the first 'cities' which consisted usually of a marketplace where people could buy/sell goods/services, surrounded by homes. The marketplace became the center of society because everybody had to go there to get the goods/services of others. As agriculture got better, fewer people were required to do it, these people created new professions and lived around the marketplace area, these eventually evolved into modern cities. the People learned to cooperate in this matter because it led to a more comfortable life. When warfare is taken into acount it is obvious that it is safer to keep the population close together to protect them, so people lived close and kept the farmlands on the outside, with stockpiles of food on the secure inside.