Apart of the [Anatomically Correct Series](https://worldbuilding.meta.stackexchange.com/questions/2797/anatomically-correct-series/2798#2798)

**Vanara**
[![Source:https://www.wikiwand.com/en/Vanara](https://i.stack.imgur.com/jWFHL.jpg)](https://i.stack.imgur.com/jWFHL.jpg)

The Vanara is a group of people who lives in the forest in the Hindu epic "Ramayana." In there, it describes them as human-like, with reference to their speech, clothing, habitations, funerals, consecrations, and abilities to form armies. It also describes their monkey-like characteristics such as their leaping, hair, fur and a tail. 

[![enter image description here](https://i.stack.imgur.com/cgMgn.png)](https://i.stack.imgur.com/cgMgn.png)

From the description, to me it sounds like they're monkeys who gained sapience instead of the great apes. What kind of evolutionary pressure would allow those kinds of events to happen? What would be the physical changes they'd need to have as well?