Answer:
To increase our survival chance.
Explanation:
In order to survive in the harsh environment, Humans generally need to do 2 things : fulfill our basic needs and defend ourselves from external threats.
Both of them would be much easier if Humans are working together in a group.
For example, during hunter/gatherer eras, catching animals that can run faster than humans will be much easier if we have teammates to surround the prey rather than working alone.
On top that, being in a group also provide better protection from the attacks of wild animals or other humans. This is why human creatures get transformed into a social being.
The Vice president in my opinion is almost a second president. The vice president's main use in this century is to replace the president in a dire emergency. This is why we almost never see the VP and President together. The president is only one man and it is almost impossible for him to do everything that is needed in the time that he is alloted in office. This is why the VP has many other duties, to help and support his partner.
