The conditions that sustain humanity are not natural and never have been. Since prehistory, human populations have used technologies and engineered ecosystems to sustain populations well beyond the capabilities of unaltered “natural” ecosystems.
Ellis mentions his learning the “classical mathematics of population growth,” only to be confronted by the simple yet overwhelming fact that populations have grown over millenia while increasing the productivity of land. He continues:
I discovered the agricultural economist Ester Boserup, the antidote to the demographer and economist Thomas Malthus and his theory that population growth tends to outrun the food supply. Her theories of population growth as a driver of land productivity explained the data I was gathering in ways that Malthus could never do.
While I am not familiar with Boserup’s work, this article has led me to be intrigued about it. In any event, the article could be well worth your time.