Evolving with our stomachs : We no longer have to hunt our food; is that a good thing?

Sometimes progress really does appear in the numbers. Consider what we spend to fill our tables.

Since 1929, the percentage of disposable income that the typical American spends on food has been steadily dropping from about one-quarter of our available cash to just 10 percent. Quite simply, it takes less for us to feed ourselves than virtually any other people on Earth.

Technology has been revolutionary in its ability to help us obtain and store food. But essential tools like refrigeration and long-haul transit have only been feasible for the past 150 years, barely a speck in the long view of human history.

Even the advent of organized agriculture and the domestication of food animals, which took place about 10,000 years ago by most estimates, was just a tick on the evolutionary clock. Most modern sources of calories simply weren't available to prehistoric hunter-gatherers.

In other words, we, meaning most residents in highly technological nations like the United States, are truly among the first handful of generations never to worry about where to get our food.

"This is the first time in human history that's been the case for large numbers of people," says George Mason University professor Peter Stearns, author of "Fat History."

Built for famine
Modern life may have solved most of our food-gathering problems, but human evolution has not kept up. Our bodies are still wired for hunter-gatherer biology: Eat all the food you can and store it — in body fat — in case your supply of food runs out, as in the case of famine. A dangerous configuration for a society with all-you-can-eat buffets.

Our ancient ancestors, especially those on the African plains, hunted far leaner animals than we now eat — species closer to modern deer and elk than the typical meat cow. Processed grains and sugars have no counterparts in ancient foods.

And modern taste combinations like concentrated fat (butter) and concentrated sweetness (sugar) rarely co-exist in nature, notes Loren Cordain, professor of health and exercise science at Colorado State University.

"You get fat on the types of foods that have been introduced since the agricultural revolution," says Cordain, author of "The Paleo Diet," which advocates emulating prehistoric eaters. Think South Beach without any grains, salt or sugar, and lots of fish and broccoli.

Outpacing biology
Cordain argues that when it comes to food, evolutionary mechanisms simply can't match the fast pace of human innovation. The result in the United States, he suggests, is heart disease and Type 2 diabetes, to say nothing of obesity.

Not every anthropologist goes so far, but most acknowledge that rich nations are all but drowning in food. And as developing nations grow, people once threatened by famine are quickly facing the opposite problem.