Voice 1: Some scientists think that the damaged genes may be the ones that cause human beings to walk on two legs. If that is true, it would explain why the five young people cannot walk normally. These scientists think that other genes may have started working instead of the damaged genes. The scientists suggest that these genes are 'older'. They may be the genes that cause animals to walk on all four legs. They think that these genes could have existed in our ancient ancestors.
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