What happened when the human population increases past sustainability

Overpopulation can result from an increase in births, a decline in mortality rates, an increase in immigration, or an unsustainable biome and depletion of resources.

Many of the problems associated with overpopulation are explored in the dystopic science fiction film Soylent Green, where an overpopulated Earth suffers from food shortages, depleted resources and poverty and in the documentary Aftermath: Population Overload, which explores what would happen if the human population suddenly doubled in size.

b.have there own function.