Our own two feet

Why did early humans begin to walk on two feet?

The reasons that Humans began walk on two feet were:

1. To be able to carry more food, to seem attractive to the females in order to mate
2. To be able to use more tools
3. To be able to pass the savannas
4. To run faster in order to hunt better

Some of these theories were disproved, but we now still do not know the reason that humans started to walk upright on two feet.