A comparison of images of dentitions from human (left), Ar. ramidus (middle), and chimpanzee (right), all males are shown in this image released to Reuters on October 1, 2009. Below are corresponding samples of the maxillary first molar in each. Red, thicker enamel (~2 mm); blue, thinner enamel (~0.5 mm). Contour lines map the topography of the crown and chewing surfaces. The skeleton of an early human who lived 4.4 million years ago shows that humans did not evolve from chimpanzee-like ancestors, researchers reported on Thursday. In a special issue of Science, an international team of scientists has for the first time thoroughly described Ardipithecus ramidus, a hominid species that lived in what is now Ethiopia. REUTERS/Science/AAAS/Handout (UNITED STATES ENVIRONMENT SCI TECH) FOR EDITORIAL USE ONLY. NOT FOR SALE FOR MARKETING OR ADVERTISING CAMPAIGNS
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