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Chimpanzees and humans are more different than previously thought, based on a draft of the chimp genome published in the September 1 Nature. Although the human genome differs from our closest relative's by 1.2 percent in terms of single nucleotide changes, the international Chimpanzee Sequencing and Analysis Consortium finds that duplications and rearrangements of larger DNA stretches add another 2.7 percent difference. Seven regions in the human genome that differ from that of chimps bear strong hallmarks of natural selection; for instance, one contains elements regulating a gene implicated in nervous system development and another possessing genes linked with speech. Consortium glycobiologist Ajit Varki and his colleagues also report in the September 9 Science the first human-specific protein, which binds to cellsurface sugars and is expressed in brain cells known as microglia. These immune cells are involved in ailments not seen in chimps, such as Alzheimer's, multiple sclerosis and HIV-induced dementia.