A study from U.S. and Chinese researchers suggests Neanderthals and early modern humans probably had similar cognitive abilities Neanderthals and humans have differently shaped skulls, which scientists have long assumed meant they also had different brains. But new research challenges that assumption. Mike Kemp / In Pictures / Getty Images Neanderthals lived for hundreds of thousands of years before mysteriously disappearing around 40,000 years ago—and scientists have long puzzled over what caused their extinction. One possible explanation is that, based on the size and shape of their skulls, Neanderthals may have been less intelligent than early modern humans. According to this theory, when Homo sapiens arrived in Europe and Asia, they used their superior smarts to outcompete Neanderthals. But new research, published last month in the Proceedings of the National Academy of Sciences , challenges this idea.…