What are the possible reasons why forest apes can evolve into humans?

Because the temperature in some parts of the earth changed tens of thousands of years ago, such as plate orogeny, the forest area was greatly reduced, and some forest apes were forced to live in the fields, making it possible for them to walk upright. Of course, it takes tens of thousands of years to walk on all fours until they are completely upright. During this period, they will use some simple tools, so that their brains will be exercised and become smart. They will work together and make holes together. They improved their viability. They learned to eat with fire and barbecue food, which improved their physique. More importantly, they can not only use tools, but also make tools, which greatly improves their ability to conquer and transform nature, and gradually produces language in the division of labor and cooperation. Therefore, the change of environment forces them to live underground. 2. They can walk upright. 3. They can use tools and make tools. The brain is developed. 5. Using language, forest apes gradually evolved into humans. Those forest apes whose environment has not changed much have now evolved into apes. I hope my answer can help you. Have a nice day. Goodbye!