Why human walking in two legs?

I was wondering why we humans use two legs and all other animals use four legs to walk. I thought that I'm crazy to think about this kind of unwanted thoughts, but just before I googled it and found that University of Arizona did expensive research about this. As per research, we started walking in two legs about some millions years ago, and this is the first revolution of human kind. Our brain got much stronger because of this change. Because if we continue walking in four legs, we spend more energy for walking and lot of energy consumed by just for walking activity. Our brain itself consumes 20% of energy and if we stand up and start walk blood circulation to brain increases and more oxygen to brain hence we can generate more ideas. So after started walking in two legs,we advanced our innovation and science discoveries quite a lot. Just imagine if we keep on walking four legs and we spend lot of energy for walking, our blood circulation to brain decreases, and we can not advance like this. So if you want to generate more ideas, just walk and walk and walk, not four legs though.

Happy long weekend.