The new jawbone: its teeth are smaller than those of other human relatives Scientists have unearthed the jawbone of what they claim is one of the very first humans. The 2.8 million-year-old specimen is 400,000 years older than researchers thought that our kind first emerged. The discovery in Ethiopia suggests climate change spurred the transition from tree dweller to upright walker. The head of the research team told BBC News that the find gives the first insight into "the most important transitions in human evolution". Prof Brian Villmoare of the University of Nevada in Las Vegas said the discovery...