[Eugenics Alert]: The Populations Problem « Center for the Advancement of the Steady State Economy

"Likewise, human organisms might be genetically redesigned to require less food, air, and water. Indeed smaller people would be the simplest way of increasing metabolic efficiency (measured as number of people maintained by a given resource throughput). To my knowledge no one has yet suggested breeding smaller people as a way to avoid limiting births, but that probably just reflects my ignorance. We have, however, been busy breeding and genetically engineering larger and faster-growing plants and livestock. So far, the latter dissipative structures have been complementary with populations of human bodies, but in a finite and full world, the relationship will soon become competitive.
http://steadystate.org/populations-problem/