This came in the Mail today..Read on...
Sahel is the transition region of grassland and shrubland between wooded Africa to its South and Sahara to its north.
This is the where the modern humans evolved, after chimps from the wooded south travelled northwards and started bi-pedalism and hunting for small prey and developed the first tools for cooking and hunting. Jaw size became smaller as the cooked food became available. And brain size and processing increased due to additional proteins available from hunted food. Anthropologists are unanimous in view after studying dietary habits and tools made by first humans in the region that modern humans may not have evolved without change in dietary habits.
Read articles below from Berkeley and National Geographic.
Sahel - Wikipedia, the free encyclopedia
06.14.99 - Meat-eating was essential for human evolution, says UC Berkeley anthropologist specializing in diet "Evolving to Eat Mush": How Meat Changed Our Bodies
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Rgds
Amandeep Singh
Meat-eating was essential for human evolution, says UC Berkeley anthropologist specializing in diet
By Patricia McBroom, Public Affairs
BERKELEY-- Human ancestors who roamed the dry and open savannas of Africa about 2 million years ago routinely began to include meat in their diets to compensate for a serious decline in the quality of plant foods, according to a physical anthropologist at the University of California, Berkeley.
It was this new meat diet, full of densely-packed nutrients, that provided the catalyst for human evolution, particularly the growth of the brain, said Katharine Milton, an authority on primate diet.
Without meat, said Milton, it's unlikely that proto humans could have secured enough energy and nutrition from the plants available in their African environment at that time to evolve into the active, sociable, intelligent creatures they became. Receding forests would have deprived them of the more nutritious leaves and fruits that forest-dwelling primates survive on, said Milton.
Her thesis complements the discovery last month by UC Berkeley professor Tim White and others that early human species were butchering and eating animal meat as long ago as 2.5 million years. Milton's article integrates dietary strategy with the evolution of human physiology to argue that meat eating was routine. It is published this month in the journal "Evolutionary Anthropology" (Vol.8, #1).
Milton said that her theories do not reflect on today's vegetarian diets, which can be completely adequate, given modern knowledge of nutrition.
"We know a lot about nutrition now and can design a very satisfactory vegetarian diet," said Milton, a professor in the Department of Environmental Science, Policy & Management.
But she added that the adequacy of a vegetarian diet depends either on modern scientific knowledge or on traditional food habits, developed over many generations, in which people have worked out a complete diet by putting different foods together.
In many parts of the world where people have little access to meat, they have run the risk of malnutrition, said Milton. This happened, for instance, in Southeast Asia where people relied heavily on a single plant food, polished rice, and developed the nutritional disease, beriberi. Closer to home, in the Southern United States, many people dependent largely on corn meal developed the nutritional disease, pellagra.
Milton argues that meat supplied early humans not only with all the essential amino acids, but also with many vitamins, minerals and other nutrients they required, allowing them to exploit marginal, low quality plant foods, like roots - foods that have few nutrients but lots of calories. These calories, or energy, fueled the expansion of the human brain and, in addition, permitted human ancestors to increase in body size while remaining active and social.
"Once animal matter entered the human diet as a dependable staple, the overall nutrient content of plant foods could drop drastically, if need be, so long as the plants supplied plenty of calories for energy," said Milton.
The brain is a relentless consumer of calories, said Milton. It needs glucose 24 hours a day. Animal protein probably did not provide many of those calories, which were more likely to come from carbohydrates, she said.
Buffered against nutritional deficiency by meat, human ancestors also could intensify their use of plant foods with toxic compounds such as cyanogenic glycosides, foods other primates would have avoided, said Milton. These compounds can produce deadly cyanide in the body, but are neutralized by methionine and cystine, sulfur-containing amino acids present in meat. Sufficient methionine is difficult to find in plants. Most domesticated grains - wheat, rice, maize, barley, rye and millet - contain this cyanogenic compound as do many beans and widely-eaten root crops such as taro and manioc.
Since plant foods available in the dry and deforested early human environment had become less nutritious, meat was critical for weaned infants, said Milton. She explained that small infants could not have processed enough bulky plant material to get both nutrients for growth and energy for brain development.
"I disagree with those who say meat may have been only a marginal food for early humans," said Milton. "I have come to believe that the incorporation of animal matter into the diet played an absolutely essential role in human evolution."
Milton's paper also demonstrates that the human digestive system is fundamentally that of a plant-eating primate, except that humans have developed a more elongated small intestine rather than retaining the huge colon of apes - a change in the human lineage which indicates a diet of more concentrated nutrients.
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"Evolving to Eat Mush": How Meat Changed Our Bodies
Hillary Mayell, for
National Geographic News February 18, 2005
Meat-eating has impacted the evolution of the human body, scientists reported today at the American Association for the Advancement of Science's annual meeting in Washington, D.C.
Our fondness for a juicy steak triggered a number of adaptations over countless generations. For instance, our jaws have gotten smaller, and we have an improved ability to process cholesterol and fat.
Our taste for meat has also led us into some trouble—our teeth are too big for our downsized jaws and most of us need dental work.
"It's really amazing what we know now that we didn't know 15 or 20 years ago," said Mark Teaford, a professor at Baltimore's Johns Hopkins University. Teaford helped organize a panel discussion on human diet from a number of perspectives:
• How did the ability to eat meat shape the evolution of humans?
• What can we learn about early humans from tooth shape?
Carnivorous humans go back a long way. Stone tools for butchering meat, and animal bones with corresponding cut marks on them, first appear in the fossil record about 2.5 million years ago.
How Did Meat-Eating Start?
Some early humans may have started eating meat as a way to survive within their own ecological niche.
Competition from other species may be a key element of natural selection that has molded anatomy and behavior, according to Craig B. Stanford, an ecologist at the University of Southern California (USC).
Stanford has spent years visiting the Bwindi Impenetrable Forest National Park in Uganda, Africa, studying the relationship between mountain gorillas and chimpanzees.
"It's the only forest where mountain gorillas and chimps both live," he said. "We're trying to understand the ecological relationship—do they compete for food, for nesting sites?"
The key difference between chimps and gorillas ecologically is that chimps eat meat and gorillas don't. A total herbivore is able to coexist with an omnivore because they have significantly different diets.
When humans switched to meat-eating, they triggered a genetic change that enabled better processing of fats, said Stanford, who has worked extensively with gerontologist Caleb Finch of USC.
"We have an obsession today with fat and cholesterol because we can go to the market and stuff ourselves with it," Stanford said. "But as a species we are relatively immune to the harmful effects of fat and cholesterol. Compared to the great apes, we can handle a diet that's high in fat and cholesterol, and the great apes cannot.
"Even though we have all these problems in terms of heart disease as we get older, if you give a gorilla a diet that a meat-loving man might eat in Western society, that gorilla will die when it's in its twenties; a normal life span might be 50. They just can't handle that kind of diet."
Diet and Teeth
Tool-use no doubt helped early humans in butchering their dinners. But there is evidence that the advance to cooking and using knives and forks is leading to crooked teeth and facial dwarfing in humans.
Today it's relatively rare for someone to have perfectly straight teeth (without having been to the orthodontist). Our wisdom teeth don't have room to fit in the jaw and sometimes don't form at all, and the propensity to develop gum disease is on the increase.
"Virtually any mammalian jaw in the wild that you look at will be a perfect occlusion—a very nice Hollywood-style dentition," said Peter Lucas, the author of
Dental Functional Morphology and a visiting professor at George Washington University in Washington, D.C. "But when it comes to humans, the ideal occlusion [the way teeth fit together] is virtually never seen. It's really the only body part that regularly needs attention and surgery."
Lucas argues that the mechanical process of chewing, combined with the physical properties of foods in the diet, will drive tooth, jaw, and body size, particularly in human evolution.
Essentially, by cooking our food, thereby making it softer, we no longer need teeth big enough to chow down on really tough particles. By using knives and forks to cut food into smaller pieces, we no longer need a large enough jaw to cram in big hunks of food.
"We're evolving to eat mush," said Bernard Wood, a paleoanthropologist at George Washington University.
Is this your take?
