Finishing my introduction

Hello!! Since I've last posted, I've been thinking a bit on how I could improve on what I wrote previously. One thing I've decided to do is to define words before listing them in the post.  

Bipedality: having two legs

Thermoregulation: an organism's ability to maintain an average body temperature

Primates: a group of mammals including monkeys, apes, lemurs, and humans

So, many factors went into play as we evolved into modern humans. Anthropologists have different theories as to how and why we evolved in the first place, but I'll only list the main, important ones.

Before we get to theories, though, we should talk about something we've accidentally ignored all this time - the climate! During this time, a global cooling was taking place, and it was affecting the environment big time. Rainforests were transitioning into grasslands, and grasslands were transforming into dry, uninhabitable deserts. Make sure to keep this in mind while reading through theories, as climate plays a large role in our evolution. I'll now list below the theories of why humans evolved. 

                    

            1) (General hypothesis) When Savannah's and grasslands came about, there were a lot less trees, so four legs weren't as useful as they once were. For example, there were no more trees to climb or branches to swing from. Therefore, we evolved into two-legged mammals. 

      

             2) Predation hypothesis: Bipedality allowed for greater vision above tall grasses, as you could stand up taller and watch for predators. Ironically, this also let humans gain the upper hand against predators, and they used their height to prey on animals who once used to prey on them. This greatly aided in human survival. 

              3) Endurance running: (this relates to hypothesis #2): Because bipedality allowed for running faster and greater distances, humans had access to more space for living, resources, and were able to outrun predators. This allowed them to become predators themselves as well. 

              4) Thermoregulation hypothesis: In forests, trees blocked the sunlight from reaching the animals living on the ground, so being quadrupedal wasn't a problem. However, when these forests transitioned into savannah's, the primates' backs (which contained a large surface area) were being exposed to sunlight, overheating them. Adding on to this, they were lower to the ground, which meant less air circulation. As you can imagine, these conditions would have been hard to live in. 

Therefore, this hypothesis states that because many trees didn't exist anymore to block out sun in grasslands, humans evolved to be bipedal. Bipedality allowed for their body temperatures to be regulated and prevented them from overheating under the sun, as they were now vertical. 

                  5) Load carrying hypothesis: Walking on two legs allowed for the arms of primates to be free. In these arms, they could carry more resources from place to place, such as food. They were previously confined to live where they could find abundant food, but now that they had a means to carry food, water, and other resources from place to place, they found they had access to a greater amount of land, and had more freedom to move wherever they wanted. 

^Ok that is all for hypotheses! Obviously just one hypothesis did not affect the whole of human evolution. Instead, all these hypotheses went into play in helping us evolve into who we are today.