The desiccated skin and hair of mummies from the Nubian Desert reveal what ordinary Nubians ate a millennium or two ago. The Nubians were kings once: they built pyramids and temples, carved delicate statues and jewelry, controlled trade along the Nile, and for a century or so, beginning in the eighth century B.C., even ruled Egypt, their neighbor to the north. Mostly, though, the Nubians have been pawns, invaded by the Persians and Assyrians, dominated by the Egyptians -- and finally flooded. When the Aswân High Dam was completed in 1970, the reservoir it created inundated thousands of square miles of land along the banks of the Nile, from Egypt south into the Sudan. Nearly all of what was once the Lower Nubian heartland is now Lake Nasser. Before the flood, however, teams of archeologists from around the world flocked to the region, hurriedly salvaging what they could of the Nubian past. They recovered tons of ancient artifacts -- including the entire Temple of Dendur, which now stands in the Metropolitan Museum of Art in New York -- and, even more remarkably, hundreds of ancient Nubians. Most of these mummies were ordinary folk, buried in the desert and accidentally preserved by the blistering heat and dry sands; their bodies dried out so fast that not only the bones but also the skin, hair, and muscle were saved from decomposition. And preserved along with the mummies, says Christine White, a physical anthropologist at the University of Western Ontario, is a record of what the ancient Nubians ate -- even in the last weeks of their lives. White gleaned that particular bit of information from the mummies’ hair. Researchers already knew that the ancient Nubians’ diet was inadequate; besides evidence of arthritis, tumors, and parasites, the mummies show clear signs of malnutrition, iron-deficiency anemia, and osteoporosis. Yet what that diet consisted of has been something of a mystery. Despite the intensive excavation, no physical evidence -- plant or animal remains -- was ever recovered. White has now extracted that physical evidence from the mummies themselves by looking at the isotope signatures of their tissue: the distinctive ratios of heavy nitrogen atoms to light ones and of heavy to light carbon that humans acquire from the plants and animals they eat. White studied 167 mummies from a site along the west bank of the Nile in the Wadi Halfa region of northern Sudan. The oldest mummies dated from the period between 350 B.C. and A.D. 350, when Lower Nubia was ruled by the Meroitic Empire of Upper Nubia. White first looked at the mummies’ nitrogen signature to find out their source of protein (which is rich in nitrogen). Grasses and the cows that eat them have a relatively low ratio of heavy nitrogen 15 to nitrogen 14; scrubs and bushes and the goats and sheep that browse on them in the Nubian Desert have a higher ratio. Most of the mummies, White found, had eaten these desert animals rather than cattle. Some had partaken more than others: male mummies contained more nitrogen 15 relative to their body weight than did females. Apparently the men of ancient Nubia got more than their fair share of the meat. The ancient Nubians did not just ranch in the desert. They also made it bloom -- and with crops that aren’t easy to grow in hot, arid conditions. The ratio of carbon 13 to carbon 12 in the mummies from the Meroitic period, says White, shows that fully 84 percent of the Nubians’ plant intake consisted of C3 foods like wheat, barley, and fruit--all of which require more water than is normally available in the Nubian Desert. (C3 plants shun the heavier carbon isotope and so have a lower isotope ratio than desert-adapted C4 plants.) The Nubians, White figures, must therefore have been irrigating their crops, probably using the ox-driven waterwheel--a sort of Ferris wheel with buckets that dumped water from the Nile into irrigation channels. It was invented in Mesopotamia and brought to Lower Nubia by Meroitic settlers. Lower Nubia, White speculates, may have been an agricultural hinterland that produced wheat and barley for Meroë. That might explain why mummies dating from after the fall of the Meroitic Empire around A.D. 350 ate about 9 percent fewer C3 plants than their forebears. When the Meroitic Empire fell, White says, the Nubians, who no longer had to grow so much wheat and barley, may have reverted to a more traditional diet of C4 plants, like sorghum and millet. Such grains are much easier to grow in the desert than C3 crops, even with irrigation. Today in the Wadi Halfa, wheat and barley are grown in the fall and winter, with the aid of irrigation and the annual flooding of the Nile, while sorghum and millet are planted in the spring and harvested beginning in early June. Could the same crop rotation, White wondered, have been occurring over a thousand years ago? The mummies’ hair said yes. Until White’s work, only bone had been used in isotopic analyses, and bone takes between 25 and 30 years to replace its store of isotopes -- making its isotope signature just a homogenized version of what was consumed over a lifetime, as White puts it. But isotopes show up in hair two weeks after they’re consumed. Thus isotope signatures from increments along a hair shaft can reveal any changes in diet that occurred while the hair was growing. White cut hair from 14 post-Meroë mummies into three-quarter- inch-long segments, each segment representing about two months’ growth. She found that the isotopic signature fluctuated dramatically between segments, indicating that the person had alternated between periods of eating mostly C3 plants and ones of relying on C4 plants. Furthermore, by looking at the hair closest to the scalp, White could tell what the future mummies had eaten just weeks before they died. Nearly two-thirds of them had been eating C4 plants. That suggested they died after the sorghum and millet harvest in June, but before the wheat and barley harvest in the winter. Why would more Nubians have died during summer? Because of heat and malnutrition, says White. C4 plants aren’t as nutritious as C3 plants; sorghum is low in vitamin B, for instance, and vitamin B deficiency increases the incidence of pellagra, a disease that causes gastrointestinal and neurological problems. Moreover, by the end of summer in Nubia, even C4 crops are scarce. Today more residents of the Nubian Desert die in summer than during any other time of year. One thousand years ago, their ancestors may have faced the same hardships.