Oh well sorry for you too
Answer:
Social values are designed to help the members of the society reach a certain level of harmony. It contains a set of principles that considered as "acceptable" or not "acceptable" which can influence the members of society to behave.
Conforming to social values tend to prevent a lot of conflict, which can lead to low level of mortality rates that cause an increase in population.
Traditional thinking that to have strong correlation with religious teachings. Most religions advocated their followers to avoid violence and have a structured set of families that will also contribute to the increase in population.
What you describe happened mostly to Africans
If Africans waged war against other nations, the other nations that won would enslave the people and sell them on the market. If they waged war between themselves, the stronger tribes would enslave the weaker tribes and sell them to the slave market even though they are more or less neighbors.