The physical factors that limit people like the are that they don’t have access to a fresh source of water and are far from a city which would help them with building. Instead of developing, they would constantly have to search for food.
With wars, supplies are being constantly used and diminished. Over time during a war, there is less time spent on developing which is used to combat each other.
In places such as China, the population can affect a lot of things as with overpopulation, the development is slowed down due to the people trying to find better ways to live instead of improving development and the economy.