Oldest Human DNA Is 400,000 Years Old, But Why Do Scientists Call Discovery 'Irritating?'

The results of a DNA test of a 400,000-year-old human thighbone are complicating what we thought we knew about human evolution. The bone, found in a cave in northern Spain known as the "Pit of Bones," is the oldest human mitochondrial material ever sequenced. But rather than reveling in their discovery, scientists are getting frustrated.