Football...

*skips on his merry way*

haha you're doing it right!

Dammit, you beat me to it. By a long shot

Most likely because east Africa conditions eons ago became cooler and drier, most likely with the coming of a new ice age, which made savanna scrub vegetation advance over tropical woodlands, thus desfavoring quadrupedal primates. Progressive mutations ended up favoring bipedal humanoids because it made easier to find food and escape predators in the open wilderness.  

Interesting to note that pratically we had only three significant changes in our skeleton on this long long way - longer legs, and some shape alteration on our pelvis. Among the minor changes are that toes became shorter because it consumes less energy on long distance runs, and shorter arms for the same reason (more stability on running).

Some features of the human skeleton remained poorly adapted compared to what it should be though. Our spine and our knees, for instance. Pain on the back and knee joint issues are going side by side with humanoids since they standed in two legs.

You forgot the most important thing, we started eating better quality diets which lead to an increased mass in our brains. Most impportantly the the cerebral cortex incereased in size. Homo Sapians especially grew in the frontal lobe which is the area of the brain that distinguishes us the most from other animals. It allows us to think logically, as well as abstractly and language would not exist without it. In all, the cerebral cortex's massize mass is what makes us human.

Great response though.

Oh yeah, this too. Interesting to note that human sapience was an evolutionary unlikely event even with better diet and developed bipedalism. You would expect one sapient species to first arise on a oxygen-rich atmospheric phase like the carboniferous was and probably on a bird (long distance locomotion, sheer 3D acrobatics, need to memorization, bird brains are much more worthy pound-per-pound than primate ones).

I was wondering when would somebody bring an answer like: "to hold a videogame controler or just to play videogames" with kinect we do not need our hands anymore do we? are we going back to the source in a sort of inverse evolution or regression.

this site is better than the sciencedaily.com

Frees our hands to create and use tools.

I saw some research that concluded the key advantage was being able to carry food long distances. Most animals have to eat food where they find it, but humans can easily kill an animal and haul it back home to safety. It lets you avoid having your kill stolen by larger predators and lets you bring home the bacon to your family.

Basically, being bipedal makes cave-dwelling and the hunter/gatherer society possible.

Just an interesting little biological note,

Did you know that the human brain, as a source of food, is the perfect balance of nutrients?

So when people back in the day cannibalized other humans, it was actually the perfect food source, they they actually did gain their power, so to speak.

Also, some species of ape ancestry are cannibals.