40, 000 years ago the steppes of Eurasia were home to our closest human relative, the Neanderthals. Recent genetic and archaeological discoveries have proven that they were not the dim-witted cave dwellers we long thought they were. In fact, they were cultured, technologically savvy and more like us than we ever imagined! So why did they disappear? We accompany scientists on an exciting search for an answer to this question and come to a startling conclusion ...