In my life time the numbers of humanity and the proportion of humanity that lives in town, conurbations and cities has increased tremendously. Cities thrive in ways that other places cannot. The demands of a mass of humanity for food, shelter, warmth and work are so overwhelming that they must huddle together, gaining comfort and succour from their mass.
I cannot but wonder that today most of humanity prefer to live cheek by jowl in cities; herds provide some protection for ruminants; cities appear to provide some protection for humans but the greatest threat to humans is humanity itslef, so massing together does no more than concentrate the problems that humanity can engender.
There is the seed of an idea here. I shall think on it.