吃肉，可能是人类长寿的关键(ZT)

Lucy, a 3.2 million-year-old Australopithecus afarensis named after the Beatles song "Lucy in the Sky with Diamonds," is perhaps the world's most famous fossil. She was discovered in the Afar region of Ethiopia in 1974 and remains among the most complete skeletons of an erect-walking human ancestor ever found, with about 40 percent of her bones intact. Her discovery allowed scientists for the first time to determine that upright walking predated the big brains of modern humans. Lucy's brain case is about the size of a chimp. In this file photo, visitors view the Lucy skeleton at a Houston museum. The exhibit is currently in Seattle.

The diminutive fossil skull of 3.5-year-old early human ancestor, known as Taung child, was hailed as the "missing link" between apes and humans when it was discovered in 1924. Known scientifically as Australopithecus africanus, the discovery of the 2 million-year-old child also provided the first evidence that early humans evolved in Africa, rather than Europe, as many scientists believed at the time. In this photo, a researcher holds a replica of the skull as he makes the case that an eagle killed the Taung child.

Turkana boy, a nearly complete 1.6 million-year-old fossil of what some scientists call Homo ergaster, an early African population of Homo erectus, is considered the most complete skeleton of a prehistoric human ever found. The boy, who was discovered in 1984 in Kenya's Turkana region, stood 5-foot 3-inches, indicating that hominids had gotten considerably taller and lankier since the days of Lucy, 3.2 million years ago. Plans to unveil Turkana boy at the National Museum of Kenya, shown here, in 2007 caused a stir between creationists and scientists.

Many cartoons of evolution show a humpbacked ape slowly, linearly, progressing to a tall and erect modern human. Scientists long ago concluded that was too simple of a view, preferring instead to use a branching, thorny and knotted tree to depict the process. A discovery announced in 2007 threw yet another splinter in the picture. Many scientists had believed Homo habilis gave rise to Homo erectus who gave rise to modern humans. But the new finding shows habilis and erectus lived side by side for half a million years, raising doubt that habilis is a direct human ancestor. The scientists also found that erectus exhibited large size variation within the species, as shown in this image comparing two erectus skulls.

The 1856 discovery of a skull cap and partial skeleton from a cave in Germany's Neander valley was the first recognized fossil human form. But exactly how the species, named in 1864 as Homo neanderthalensis, is related to modern humans remains the subject of fierce academic debate. Neanderthals occupied Europe and Asia from about 200,000 years to 30,000 years ago, overlapping in places with modern humans. Recent genetic analyses suggest little, if any, interbreeding between the species. Skeletal evidence, however, suggests Neanderthals were not very different than their modern human cousins. Even their brains were comparable to, if not bigger, than ours, as depicted in this Neanderthal reconstruction. Other studies have shown that like modern humans, Neanderthals used tools, wore jewelry, hunted, and buried their dead.