Humans have followed a Paleolithic diet for a few million years and a "modern" agricultural diet for only a few thousand years. The not too gentle forces of natural selection have spent millennia shaping and molding our evolving line, weeding out those offshoots and mutations that didn't thrive on the available fare, reinforcing those traits that improved our survival, until we emerged as modern humans some one-hundred-thousand years or so ago. Since our modern form and physiology today is the same as that of these one-hundred-thousand-year-old ancestors, it stands to reason that we should function best on the diet they - and we, their descendants - were designed to eat, not necessarily the "prudent" diet recommended by modern nutritionists, which is often composed primarily of foods that weren't even in existence for the vast majority of our time on earth. It is by turning to the vast amount of anthropological data that we can determine what our ancestors ate for the three to four million years that we have been recognizable as humans.

In a Word: Meat
In anthropological research if you follow the trail of meat consumption, you'll find the history of our earliest ancestors, because there is no real debate among anthropologists about early man's history as a meat eater and his evolution into a skilled hunter; the only debate is about when this hunting ability became fully developed.

Upon the discovery of the first fossils of our earliest upright ancestors anthropologists postulated that these creatures, the australopithecines, and those that followed until the advent of agriculture was "bloodthirsty, savage" hunters. As archeologists developed more technologically sophisticated means of analyzing their collections of bones and tools, thinking drifted from the idea of early man as hunter to that of early man as scavenger. Gone was the notion of groups of skilled hunters stalking, bringing down, and butchering large herbivores; in its place was the vision of groups of hominids coming upon the kills of large carnivores and stripping the remaining bits of flesh from the carcasses and using primitive tools to pummel and break into the cavities of the long bones and skulls to get at the marrow and brains within. The mainstream archeological and anthropological view posits that this scavenging lifestyle predominated until the last one-hundred-thousand years or so, coinciding with the arrival on the scene of anatomically modern humans. But, thanks to recent findings, this view is changing - and changing in almost flashback fashion to the ideas of the earlier anthropologists. Our ancestors from a long, long way back indeed appear to have been skilled hunters.

New excavations in Boxgrove, England, and Atapuerca, Spain, reveal that hominids as far back as five-hundred-thousand or more years ago were exquisitely skilled hunters. Archeologists at Boxgrove found evidence of numerous kill and/or butcher sites of extinct horses, rhinoceroses, bear, giant deer, and red deer - all large mammals requiring a great deal of skill and fortitude to bring down with primitive implements. Researchers know these animals were hunted and not just found and scavenged, not only because of the arrangement of bones at the butcher site, but through microscopic evidence as well. When analyzed under a microscope, the bones of scavenged carcasses typically show the cut marks from the tools of the scavengers lying over the tooth marks of the carnivores that actually made the kill, indicating that the scavenging came later. At Boxwood, archeologists found just the opposite. The cut marks from the flint tools on the bones show evidence that tendons and ligaments were severed to remove muscles from the bones. The cut marks compare to those produced by today's butchers using modern tools. In the words of Michael Pitts and Mark Roberts, two of the primary excavators at Boxgrove, "every animal for which there is any evidence of interference by the hominids has been carefully, almost delicately, butchered for the express purpose of consuming the meat."

Further evidence of hunting comes from several actual wooden spears found throughout Europe that have proven to be the oldest wooden objects of known use found anywhere in the world. Archeologists have dated an almost sixteen-inch-long spear tip carved of yew wood found in 1911 in Clacton, England, to be somewhere between 360,000 and 420,000 years old. Another spear, also made of yew, that is almost eight feet long and dated to 120,000 years old was found amid the ribs of an extinct elephant in Lehringen, Germany, in 1948. A few years ago excavators in a coal mine near Schöninger, Germany, found three spruce wood spears shaped like modern javelins, the longest of which measured over seven feet, that proved to be 300,000 to 400,000 years old. And at one of the butcher sites at Boxgrove, excavators actually found a fossilized horse scapula that shows what appears to be a spear wound.

The excavation at Boxgrove provided archeologists with another surprise. It had long been thought that such stone tools as arrowheads and hand axes, once fashioned, were carried around by their makers and used as needed, much as we do today with modern hunting knives and other camp tools. Researchers who have practiced making prehistoric tools and arrowheads from flint - flint knapping, as it's called - found the task tedious, difficult, and fraught with the constant risk that one wrong strike could destroy the tool in the making. As a result, the thinking was that the effort put into making quality stone tools was so great that the makers would surely value them and keep them as long as they could. Amazingly, it appears from the meticulous examination of these ancient sites that these hominid hunters were so adept at making flint tools for butchery that they knocked them off on the spot, used them to skillfully dismember their prey, and left them at the site rather than carry them around. And these weren't just crude flint chips; these were some of the finest flint hand axes ever found. Modern attempts to reproduce the quality of these tools have usually fallen far short of the mark. Obviously these ancient hominids were skilled enough to whip out a flawlessly made butchering tool at a moment's notice, a fact that implies a lifetime of hunting, butchering, and meat consumption.

We know from these European sites that hominids were actively hunting and eating meat as far back as five-hundred-thousand years ago, but what about before that? The earliest stone tools date to around 2.6 million years ago and have been found in association with extinct animals' bones from the same period. Some of these have cut marks with overlying carnivore teeth marks, indicating hunting, while others have carnivore teeth marks with overlying cut marks, implying scavenging. The most probable conclusion is that protohumans back at least 2.6 million years ago - a time corresponding to the appearance of the genus Homo - were engaged in the consumption of meat by either scavenging or hunting activities and probably a combination of the two.

Prior to 2.6 million years ago the human line was represented by australopithecines, which have been believed to be primarily fleshy fruit eaters. So, it was thought, the human line developed the taste for meat sometime between the plant-eating australopithecines and the appearance of Homo, but even that time frame has now been pushed back. Anthropologists Matt Sponheimer and Julia Lee-Thorp from Rutgers University and the University of Cape Town, respectively, performed an ingenious analysis on the remains of four three-million-year-old Australopithecus africanus specimens found in a cave in South Africa. Bones of this age are always fossilized, thus preventing researchers from extracting living material from them for analysis, but not so for the tooth enamel; tooth enamel persists relatively unchanged through the millenia and lends itself to testing for organic content. Whatever is incorporated into the developing enamel stays there - in this case for three million years. By testing for variations in the carbon atoms making up the tooth enamel researchers can determine what the owner of the tooth ate because different food sources contain specific carbon isotopes. When Sponheimer and Lee-Thorp analyzed the australopithecine enamel for the content of Carbon-13, a heavy isotope typically found in grasses and in the flesh of grass-eating animals, they found plentiful amounts, indicating that these hominids ate either a fair amount of grass or grass-eating animals or both. Analysis of the surfaces of the teeth, however, didn't show the specific scratches that are the telltale signs of grass eaters, leading the researchers to conclude that australopithecines at least as far back as three million years ate meat.

We have evidence tracking back three million years for meat eating by our ancestors and at least a five-hundred-thousand-year history of skillful hunting. In terms of generations this means that we modern humans are the result of one-hundred-fifty-thousand generations of meat eating, twenty-five-thousand generations of skilled hunting, but only a mere four-hundred to five-hundred generations of agriculture. Since geneticists calculate that it takes at least two-thousand generations for even minimal changes to be manifest, it should be apparent that eons of meat eating forged our physiology and metabolism to respond optimally on a diet containing significant amounts of meat. A low-fat, high-carbohydrate diet, the real fad diet in evolutionary terms, limits the consumption of the meat we were designed by nature to eat and replaces it with starchy foods that our bodies haven't had the time to adapt to. It's no wonder the low-fat diet wasn't what it was cracked up to be. It's far too new for our bodies to know what to do with.

Brain Food
Not only was meat a principal source of nutrition for developing man, it actually was the driving force allowing us to develop our large brains. For years anthropologists argued that we humans got our large brains because we had to develop them to learn hunting strategies to capture and kill game much larger, faster, and meaner than ourselves. Anthropologists Leslie Aiello and Peter Wheeler turned that idea on its head in a brilliant paper postulating that we were able to develop our large brains not to learn to hunt but because the fruits of our hunting - nutrient-dense meat - allowed us to decrease the size of our digestive tracts. The more nutrient dense the food, the less digestion it needs to extract the nutrients, and consequently the smaller the digestive tract required. (The human digestive tract, while longer than true carnivores, is the shortest of any of the primates.)