Why did early humans begin to walk on two feet?

There are many different theories to why early humans began to walk on two feet, and yet scientists are starting to think that this may be something that is simply unknowable. This is because there is no evidence or proof to why humans would have become bipedal when humans and monkeys split. The only resources we have are scientists' brains and the logical conclusions made about each theory. However, there are some things that scientists and historians can agree about - for example, that they did not start walking on two feet for intellectual reasons. Based on the studies made of the brains of early humans we know that they didn't wake up one morning and decide that "Oh, I'm so bored of crawling. It doesn't get me anywhere. I think that I'll try walking because of all of the stuff I have to get done today!"
Therefore, scientists are pretty sure that bipedality came naturally to early humans, starting at least 3 million years ago.
A theory that is not so recent yet is well known is that early humans, when creating tools, realized that they would need their hands and arms to create the tools, and for this they needed to be able to stand up. This could very well be true but there may have been a number of other reasons that early humans decided to stand up. Another theory revolves around one of the most important things in our life - food! When two early humans mated one of them needed to get food while the other parent focused on taking care of the child. Early humans may have learned how to stand up not only in order to make the tools, but also to use the tools to hunt the animals. This also may have attracted the mate even more - when someone is pregnant, the last thing they want is a mate where they have to do all of the work. This implies that the male needed to be able to hunt food and carry food properly in order to attract a mate, and in order to survive in general.
A third theory is that when early humans were migrating across savannas, they needed to stand up in order to go across the tall grass. Africa was once filled with forests, but then the forests started to rapidly disappear and early humans had to go farther and farther each time to get to more forest. In order to do this the humans had to cross the savanna. Early humans found that by standing up, they could travel much better through the tall grass, see where they were going, and notice any possible predators. Similar to this idea, early humans may have also become bipedal to cross streams and even swim in lakes.
In conclusion, there many theories out there, some more likely than others, about why early humans became bipedal. Whichever one is right, scientists know that this was a big step in the process of evolution.