Q. How many people can the Earth support?
A. It depends on the kind of lifestyle those people enjoy, says Lisa Naughton, a UW-Madison professor of geography and environmental studies.
The late 18th century English economist Thomas Malthus — one of the first to express concern about overpopulation — observed that there should be no more people in a country than can “daily enjoy a glass of wine and piece of beef for dinner.” But what if people choose tofu and beer instead?