Other common themes included ecology, environmental ethics, and an in-depth look at human population dynamics. Although Quinn himself regarded the following associations as coincidental, his philosophy is sometimes compared with deep ecology, dark-green environmentalism, or anarcho-primitivism. Quinn notably claimed that the total population of humans, like all living things, grows and shrinks according to a basic ecological law: an increase in food availability for any population yields an accompanying increase in the population's overall size. Quinn worried that popular cultural thinking ignores this reality, instead regarding civilized humans as separate from and above any such law. He identified the Neolithic Revolution as the start of human overpopulation, when civilized peoples began to practice an imperialistic world-view that denigrates nature and that relies entirely upon expansionist farming ("totalitarian agriculture"), the human population growing in proportion to the decline of the rest of the world's biomass. Quinn's warnings about population, especially in relation to food availability, have often been compared to the warnings of 19th-century economist Thomas Robert Malthus. However, while Malthus warned that excess human population precariously motivates an excess of food in order to sustain that population, Quinn considered this assessment backwards. He instead warned that excess population is the "result" of excess food. According to Quinn, the success of totalitarian agriculture is causing a catastrophic loss of biodiversity, and, even more directly, overshoot towards an eventual population crash, of which the civilized mainstream shows very little anticipation or interest.