Humans have evolved to be innovative. And we are innovative when surrounded by a lot of other people. You can't argue against human nature...
See PhysOrg: High population density triggers cultural explosions
Increasing population density, rather than boosts in human brain power, appears to have catalysed the emergence of modern human behaviour, according to a new study by UCL (University College London) scientists published in the journal Science. High population density leads to greater exchange of ideas and skills and prevents the loss of new innovations. It is this skill maintenance, combined with a greater probability of useful innovations, that led to modern human behaviour appearing at different times in different parts of the world.
