TEL AVIV, ISRAEL—Early humans were apex predators who ate mostly meat for a period of two million years, according to a statement released by Tel Aviv University. Miki Ben-Dor and Ran Barkai of Tel Aviv University and researcher Raphael Sirtoli reconstructed the Paleolithic diet through an examination of current metabolism, genetics, and physical build, and a variety of scientific disciplines, suggesting that even though human behavior changes rapidly, our bodies evolve slowly. Ben-Dor explained that modern humans have highly acidic stomachs compared to omnivores, which would have provided some protection from harmful bacteria found in old meat. The researchers also claim that modern humans have a larger number of smaller fat cells, similar to other predators. Omnivores, in contrast, have a small number of large fat cells. The modern human genome, they add, allows for the digestion of a diet rich in fats, rather than a diet rich in sugars. Archaeological evidence for the consumption of a diet rich in fat includes the chemical makeup of human fossils, and tools made to hunt large and medium-sized animals. Humans in Africa began to eat more plants some 85,000 ago, while the diets of humans in Europe and Asia made the shift about 40,000 years ago, as environmental conditions changed, Ben-Dor said. To read about the connection between diet and changes in language, go to "You Say What You Eat."