Because of the change in the way we developed muscles and skeletal system, it also gave us aching backs and sore knees, along with may other issues.
Some anthropologists argue that carrying stuff was the main reason our ancestors became bipeds. It was not possible to turn back time and see what was actually happening all those years ago, so an international team of scientists turned to what they thought was the next best thing, wild chimps. Brian Richmond of George Washington University said "These chimpanzees provide a model of the ecological conditions under which our earliest ancestors might have begun walking on two legs. Something as simple as carrying, an activity we engage in every day, may have, under the right conditions, led to upright walking and set our ancestors on a path apart from other apes that ultimately led to the origin of our kind." Researchers spent 14 months watching chimps in one of the most famous sanctuaries in the world, Kyoto University 's Outdoor Laboratory in Guinea 's Bossou Forest, where scientists have studied how chimps use tools, such as rocks, to crack nuts open and access other variety of foods. Studies showed that chimps, more often than not walked on two feet while they carried papayas and other foods in their hands, mouths, or even on their feet. That may have made sense to a chimp, but it is not easy for them to walk upright. Unlike humans, for example, a chimp can 't stand on one leg and let its leg bones carry their weight. Because its legs are structured differently, chimps can not stand on just one leg and let its leg bones carry their weight. The changes, which had taken millions of years, brought a mixed bag. It made things easier for early humans to roam larger areas, picking low hanging fruit from the trees, carrying supplies, tools, and their kids. That also made them appear larger and more intimidating. The only difference is that we still have a backbone left over from the years when our more distant ancestors were mostly horizontal, both in water and on land. It wasn 't created to work in a vertical position, which is the main reason modern humans suffer from arthritis, sore backs, slipped disks. You may be asking when did all this begin? According to the Smithsonian Institution 's Human Origins Program, it started close to six million years ago with changes in the leg bones, then came the knee, a couple of million years later. By three million years ago, according to many experts, our ancestors were for the most part, just like us, at least structurally, and moved around mostly on their two feet, which made them lose the ability to cling to branches and climb. Last year in the journal Science, researchers reported the discovery of a fossilized foot in Ethiopia that had been made for walking, not climbing trees. It is said that foot was stiff enough to push off from the ground when walking, and flexible enough to absorb the shock of touching down, it was a huge change. No