Little is known about the ape as only a few fossils are known, including this jawbone

A fossilised tooth left behind by the largest ape that ever lived is shedding new light on the evolution of apes.

Gigantopithecus blacki was thought to stand nearly three metres tall and tip the scales at 600kg.

In an astonishing advance, scientists have obtained molecular evidence from a two-million-year-old fossil molar tooth found in a Chinese cave.

The mystery ape is a distant relative of orangutans, sharing a common ancestor around 12 million years ago.

"It would have been a distant cousin (of orangutans), in the sense that its closest living relatives are orangutans, compared to other living great apes such as gorillas or chimpanzees or us," said Dr Frido Welker, from the University of Copenhagen.

Artist reconstruction of the ape

Human evolution hopes

The research, reported in Nature, is based on comparing the ancient protein sequence of the tooth of the extinct ape, believed to be a female, with apes alive today.

Obtaining skeletal protein from a two-million-year-old fossil is rare if not unprecedented, raising hopes of being able to look even further back in time at other ancient ancestors, including humans, who lived in warmer regions.

There is a much poorer chance of being able to find ancient DNA or proteins in tropical climates, where samples tend to degrade quicker.

"This study suggests that ancient proteins might be a suitable molecule surviving across most of recent human evolution even for areas like Africa or Asia and we could thereby in the future study our own evolution as a species over a very long time span," Dr Welker told BBC News.

Extinction clues

Gigantopithecus blacki was first identified in 1935 based on a single tooth sample. The ape is thought to have lived in Southeast Asia from two million years ago to 300,000 years ago.

Many teeth and four partial jawbones have been identified but the animal's relationship to other great ape species has been hard to decipher.

The ape reached massive proportions, exceeding that of living gorillas, based on analysis of the few bones that have been found.

It is thought to have gone extinct when the environment changed from forest to savannah.