SHE was a little girl — or perhaps a little boy — who has been dead for 1000 years but a team of modern scientists is not going to let her down.

The jawbone of a toddler aged three to five, found among the kelp on Mona Vale beach three weeks ago, has been matched to a skull that washed ashore exactly six years ago.

Adding to the mystery: the bones are not Aboriginal.

As detectives from the northern beaches local area command continue to investigate how the bones ended up on the beach, forensic scientists with NSW Health Pathology are determining with staggering detail just where the child came from.

Early radio carbon-dating set the skull as coming from between 1200AD and 1400AD but yesterday the forensic pathologists confirmed they had dated it to the year 1001, give or take 30 years.

It probably belonged to a young girl, but could be a boy, of either Asian or Pacific Islander origin.

media_camera The skull has been carbon-dated to close to the year 1001. Picture: Supplied

One theory is the bones could have been part of a skeleton used by medical students, but there is no evidence of a screw hole in the top of the skull from where it would have hung.

Another is that the bones may have been washing around in the ocean for 1000 years — but then the skull would not have been in such pristine condition.

Dr Mallett said other child bones could have been washed up without anyone realising they were human.

If you look at the mandible, what look like little stones on the bottom are the adult teeth coming in, which happens at three, four and five years’ old,

- Dr Xanthe Mallett

One theory no one is considering is the child was a migrant almost 800 years before the British and went on to die on Australian soil.

“People used to collect bones, which is awful to even think about today, but they used to go around the world picking up specimens and this could have been part of a private collection,” said Dr Xanthe Mallett, anthropologist and senior lecturer in forensic criminology at the University of New England.

“It may have gone missing overboard from an early ship or, and this is completely hypothetical, the person who had the skeleton may have decided to give it the burial it never had and buried it on a beach where it was washed into the water.”

media_camera A Bone was found on Mona Vale beach also known ad the Basin north of the pool. Police conduct searches at the pool & on the beach for any more. Unknown if its human yet. Pic John Grainger

Dr Mallet said the jawbone was easily recognisable as that of a toddler aged between three and five.

“If you look at the mandible, what look like little stones on the bottom are the adult teeth coming in, which happens at three, four and five years’ old,” she said.

The skull is so well preserved that the paper-thin, delicate bones that would have surrounded the soft tissue in the eye socket can still be seen.

media_camera The skull was found six years ago on the same beach.

“It looks as thought it has been in a protective environment and may have been used as a specimen because it does look as though it has been mishandled,” she said.

“People tend to pick up skulls by putting their fingers through the eye sockets, and there is some evidence of this, rather than the correct way, which is putting your hand under the back of the cranium.”

As tests continue, Northern Beaches LAC crime manager Detective Inspector Craig Wonders said no one had come forward to claim the skull and there had been no reported thefts of medical specimens.