The advantage of walking on two legs is that we conserve a lot more energy. So where do we use this extra energy? Reproduction and adaptation.
The ability to reproduce offspring and conserve energy allows for an animal to adapt to new surroundings and environment. Of all Earthlings, humans inhabit more of this planet than any other creature. This does not mean that humans are the most populous; but humans live can survive in many conditions that many other animals can not. For example, many of the fish which live in the waters of the Pacific Coast have a temperature range tolerance of a few degrees. Raise or lower the average temperature by just three degrees, and whole species will die. Take microbes that live near volcanic vents away from the ocean deep setting, and they will die. Put a human in the Arctic, and it can survive. Put one in the rainforest, and it will survive.
Why? Because we can adapt like no other animal.
And why can we adapt so well? Because we have an ability to think. The ability to solve problems is known as intelligence. The better one can solve a problem more efficiently, the more intelligent it is. Humans have an uncanny ability to solve most problems better than any other creature on this planet.
Many people have said that it is our ability to create, rather than destroy, which separates us from the other animals. We build shelter to protect us from the cold. Okay then, what do you call birds' and beavers' nests?
Some people say it is our ability to use tools. Last I heard, several primate species use sticks to collect ants to eat, and otters use rocks to break open nuts. That's tool usage. And one form of backward usage of a tool is when birds of prey drop their catch from a high altitude to kill their prey on the rocks below.
There are many things, however, which does help define our separation from the other animals. One is that humans are the only animal which has invented God, or gods.
Another is our ability to group ourselves together in a community which can totally hate another group simply because it has a different set of beliefs, different skin color, or different way of communicating.
People refuse to allow themselves the idea that another human is still, indeed, a human, even though their eyes may not look the same, or their skin is lighter/darker, or their God is called something else.
You don't see German Shepherds disdaining Rottweilers and Chihuahuas just because they are different shapes and sizes, do you?
And many schools of fish don't mind a shark swimming in their presence when that shark is not hungry.
Humans have the ability to hate.
That's what separates us from the rest of Earthlings.