During the last American food-and-gas-price crisis, in the 1970s, one of my colleagues on the Berkeley student newspaper told me that he and his semi-communal housemates had taken a vote. They'd calculated they could afford meat or coffee. They chose coffee. The decision was slightly less effete than it sounds now, the Starbucks clone wars were still some years off, so he was talking about choosing Yuban over ground chuck. But it nonetheless said something about us as spoiled Americans. Riots were relatively 'common in Berkeley in those days. But they were never about food. (That particular revolution was starting without us on Shattuck Avenue, where Chez Panisse had just opened.) However, elsewhere on the globe, people were on the edge of starvation. Grain prices were soaring, rice stocks plummeting. In Ethiopia and Cambodia, people were well over the edge, and food riots helped lead to the downfall of Emperor Haile Selassie and the victory of the Khmer Rouge. Now it's happening again. While Americans grumble about gasoline prices, food riots have seared Bangladesh, Egypt and African countries. In Haiti, they cost the Prime Minister his job. Rice-bowl countries like China, India and Indonesia have restricted exports and rice is shipped under armed guard. And again, Thomas Malthus, a British economist and demographer at the turn of the 19th century, is being recalled to duty. His basic theory was that populations, which grow geometrically, will inevitably outpace food production, which grows arithmetically. Famine would result. The thought has underlain doomsday scenarios both real and imagined, from the Great Irish Famine of 1845 to the Population Bomb of 1968. But over the last 200 years, with the Industrial Revolution, the Transportation Revolution, the Green Revolution and the Biotech Revolution, Malthus has been largely discredited. The wrenching dislocations of the last few months do not change that, most experts say. But they do show the kinds of problems that can emerge. The whole world has never come close to outpacing its ability to produce food. Right now, there is enough grain grown on earth to feed 10 billion vegetarians, said Joel E Cohen, professor of populations at Rockefeller University and the author of How Many People Can the Earth Support? But much of it is being fed to cattle, the S.U.V.'s of the protein world, which are in turn guzzled by the world's wealthy. Theoretically, there is enough acreage already planted to keep the planet fed forever, because 10 billion humans is roughly where the -United Nations predicts that the world population will plateau in 2060. But success depends on portion control; in the late 1980s, Brown University's World Hunger Program calculated that the world then could sustain 5.5 billion vegetarians, 3.7 billion South Americans or 2.8 billion North Americans, who ate more animal protein than South Americans. Even if fertility rates rose again, many agronomists think the world could easily support 20 billion to 30 billion people. Anyone who has ever flown across the United States can see how that's possible: there's a lot of empty land down there. The world's entire population, with 1,000 square feet of living space each, could fit into Texas. Pile people atop each other like Manhattanites, and they get even more elbow room. Water? When it hits $150 a barrel, it will be worth building pipes from the melting polar icecaps, or desalinating the sea as the Saudis do. The same potential is even more obvious flying around the globe.