in what ways is the density of a population important?

Answer 1

Survival: a population that is insufficiently dense will vanish as individuals die without reproducing, e.g. a non-parthogonetic species with no male and female close enough to mate. Contrariwise, a population that is too dense may quickly exhaust its resources, e.g. people shut in a small airtight room, or predators that eliminate the prey they depend on for food.

Human populations adapt to increased density culturally, by institutionalizing behaviours such as meditation, pacifism, obedience to authority, etc. Individuals have different needs for space or companionship that relate to population density - some prefer living hermit-like surrounded by nature (Thoreau?), others prefer discotheques and cocktail parties.

I have read that increasing human population increases the number of geniuses who improve our general prospects of survival and life quality by solving complex problems - such as those posed by overpopulation. Seems a bit circular, eh?