By Bruce Bower
4
Human evolution appears poised for a scientific makeover, as unexpected and provocative findings have raised new questions this year about two poorly understood periods leading to the emergence of Homo sapiens.
The biggest conundrum comes courtesy of the oldest known DNA sample from a member of the human evolutionary family — a 400,000-year-old leg bone previously found in a cave in northern Spain. A nearly complete sample of maternally inherited mitochondrial DNA linked the bone to the Denisovans, mysterious genetic cousins of Neandertals who lived in Siberia at least 44,000 years ago (SN: 12/28/13, p. 8).