Proteins from 400,000-year-old Homo erectus fossils, specifically teeth found in China, have been analyzed and appear to show genetic links to both Denisovans and modern humans. The findings suggest a possible connection between these ancient species and modern humans, with some indications of potential interbreeding between Homo erectus and Denisovans. The discovery provides new insights into the human family tree, revealing deep genetic ties between these ancient species and modern humans.