A digital reconstruction of a million-year-old skull suggests humans may have diverged from our ancient ancestors 400,000 years earlier than thought, and in Asia, not Africa, a study said on Friday.

Findings are based on a reconstruction of a crushed skull discovered in China in 1990, and have the potential to resolve the longstanding “Muddle in the Middle” of human evolution, researchers said. But experts not involved in the work cautioned that the findings were likely to be disputed, and pointed to ongoing uncertainties in the timeline of human evolution.