how much space does man need?

the question today was, "if you brought the entire population of the world together in one space, how much land would that require?"  i think the question started with me stepping back from the scurry of day to day life in the world, listening to the noise and watching the actions and reaction of people.  it lead me to wondering why there is so many problems with man on the planet?    as a species we feel we are the biggest and the best, yet, i kept thinking of the size of the universe and simply wondered about the "how much space"  question.  if you have close to seven billion people, how big of a space would it require for everyone to sit down together, share a coffee/tea and meet their neighbor.   it turns out, if you put everyone on a stool and sat everyone on earth together in one spot, everyone could fit in the area the size of the island of puerto rico.  of course there is a variance based on how much of a junk food diet the people eat every day.

i wonder if man thinks we are living in liquid and will simply expand to whatever space is available, instead of what we need?