Psychology homework

Wat ch this extraordinary video to see the indisputable survival benefit of being a valued member of the group: http://www.youtube.com/watch?v=LU8DDYz68kM

• How did being a valued member of the group affect survival in this case?
• How might having been a valued member of a human group in our evolutionary past have led to similar survival advantage?
• Does this give use clues as to why humans became creatures born with such intense social instincts (including social emotions, social anxiety, need to be liked and valued, etc)?