In 1998, the skeleton of a 29,000-year-old child was unearthed in Portugal’s Lapedo valley.
The child had both early modern human and Neanderthal features, including the chin and lower arms of a modern human but the jaw and build of a Neanderthal.
Researchers believed that the child's anatomy was the result of mixed Neandertal-early modern human ancestry.
Now new archaeological and DNA techniques may hold the answer.