The Paleo Diet - Loren Cordain [24]
At first, humans were not terribly good hunters. They started out as scavengers who trailed behind predators such as lions and ate the leftovers remaining on abandoned carcasses. The pickings were slim; ravenous lions don’t leave much behind, except for bones. But with their handy tools (stone anvils and hammers), our early ancestors could crack the skulls and bones and still find something to eat—brains and fatty marrow.
Marrow fat was the main concentrated energy source that enabled the early human gut to shrink, while the scavenged brains contained a specific type of omega 3 fat called “docosahexaenoic acid” (DHA), which allowed the brain to expand. Docosahexaenoic acid is the building block of our brain tissue.
Without a dietary source of DHA, the huge expansion of our brain capacity could never have happened. Without meat, marrow, and brains, our human ancestors never would have been able to walk out of tropical Africa and colonize the colder areas of the world. If these people had depended on finding plant foods in cold Europe, they would have starved. In a landmark series of studies, my colleague Mike Richards, at Oxford University, studied the bones of Paleolithic people who lived in England some 12,000 years ago. Their diet, Richards confirmed, was almost identical to that of top-level carnivores, such as wolves and bears.
Hunting Big Game
Why would any sane person get close enough to poke a spear into a sharp-hoofed, kicking, and snorting 600-pound horse—much less a raging 5-ton mammoth? Why didn’t Paleolithic people play it safe, gathering berries and nuts and snaring rabbits, rodents, and small birds? Again, the wisdom of the old ways becomes clear.
The basic idea of foraging for food—whether you’re a human, a wolf, or even a house cat chasing a mouse—is simple. You’ve got to receive more energy from the food you capture than you use in trying to capture it. If you run around all day and use up 1,000 calories, but come home with only ten apples worth a grand total of 800 calories, you’re going to be very hungry. So when Paleolithic people went looking for food, they tried to get the most bang for the buck. The best way to do this, they found, was with a large animal. It takes a lot more energy to run down and capture 1,600 one-ounce mice than it does to kill a single deer weighing 100 pounds (1,600 ounces). But there’s a much more important reason why larger animals were preferred. It’s called “protein toxicity.”
We can only tolerate a certain amount of protein at a time- about 200 to 300 grams a day. Too much protein makes us nauseated, causes diarrhea, and eventually can kill us. This is why our Paleolithic ancestors couldn’t just eat lean muscle meat. They needed to eat fat along with the lean meat, or they needed to supplement the lean meat with carbohydrates from plant foods. Early explorers and frontiersmen in North America knew this, too. They were painfully aware of the toxic effect of too much lean protein; they called the illness “rabbit starvation.”
On average, large animals like deer and cows (or, for Paleolithic people, mammoths and wild horses) contain more fat and less protein than smaller animals like rabbits and squirrels. The squirrel’s body is 83 percent protein and 17 percent fat; the mule deer’s body is 40 percent protein and 60 percent fat. If you ate nothing but squirrel, you would rapidly exceed the body’s protein ceiling, and like those early pioneers, you’d end up with rabbit starvation. On the other hand, if you only had deer to eat, you’d be doing fine. You would not develop protein toxicity because you’d be protected by the deer’s higher fat content. This is why Paleolithic hunters risked their lives hunting larger animals.
In the Paleo Diet, you’re protected from protein toxicity, too—by unlimited access to fresh fruits and vegetables. You’re also protected by the good cholesterol-lowering monounsaturated fats and by our most powerful deterrent to heart disease—omega 3 fatty acids. With these