An ancient child of a long-extinct human-like species from 104,000 years ago in northern China had teeth that grew in a similar way to modern-day humans.
Remains of the ancient six-year-old child, known as the Xujiayao juvenile, were first found in the 1970s and reanalysed.
Evidence found the dental development was very similar to what is seen in young children today.
Both the archaic hominid and modern Homo sapiens have a prolonged period of infantile dependency on others to survive.
Debbie Guatelli-Steinberg, co-author of the study and professor of anthropology at The Ohio State University, said: ‘The Xujiayao juvenile is the oldest fossil found in east Asia that has dental development comparable to modern humans,’ Guatelli-Steinberg said.
‘It may suggest that these archaic humans had a slow life history like modern humans, with a prolonged period of childhood dependency.’
Growth lines in the teeth were well preserved and these provide a record of dental development.
Modern humans take far longer to develop their adult teeth than our primate relatives and it is believed this is due to a longer period of child dependency.
Researchers used synchrotron X-ray imaging to look inside the fossil to see the internal structure of the teeth and study the rate of tooth development.
Although the teeth resemble modern humans, the rest of the skull does not, scientists say.