The ancient human "could be described as an ape-man" according to professor Per Ahlberg at Uppsala University. It was a sub-species of homo erectus, the first early human to spread out beyond Africa, over 800,000 years ago.
The story of how this specimen of so-called Peking Man survived is bound up with the war-torn history of China. Swedish paleontologists were the first to search for these kinds of remains, in the 1920s. Hundreds of large boxes were filled with material dug up in China. But not all of the boxes were investigated - the tooth lay long forgotten for over 50 years. Meanwhile in China itself the skulls and other large bones of Peking Man were lost during the Second World War.
Only a handful of fragments, including some teeth, remain to prove that Peking Man ever existed.
Being forgotten may make the Uppsala tooth more valuable, says Per Ahlberg, professor of evolutionary developmental biology at Uppsala University. Since the tooth has not been cleaned it will give researchers clues about what the long-vanished humans used to eat.