Why are the mountains thinly populated? Answer long in points . Please!

The main reason why mountains are rarely populated is because of the harsh climate that are dominating in those areas. On the other side, another important reason is that mountainous areas are not fertile enough and people are not able to grow crops. Lack of resources therefore is obliging people to move from the mountains to lower terrains.

Explanation:

Because of the mentioned reasons most of the people since the beginning of civilization were inhabiting river valleys and the areas that have better climate.

For example, Chinese civilization developed in the valley of Yangtze and Huang He and not Himalayas.