It appeared to be one of archaeology's most sensational finds. The skull fragment discovered in a peat bog near Hamburg was more than 36,000 years old - and was the vital missing link between modern humans and Neanderthals.

This, at least, is what Professor Reiner Protsch von Zieten - a distinguished, cigar-smoking German anthropologist - told his scientific colleagues, to global acclaim, after being invited to date the extremely rare skull.

However, the professor's 30-year-old academic career has now ended in disgrace after the revelation that he systematically falsified the dates on this and numerous other "stone age" relics.

Yesterday his university in Frankfurt announced the professor had been forced to retire because of numerous "falsehoods and manipulations". According to experts, his deceptions may mean an entire tranche of the history of man's development will have to be rewritten.

"Anthropology is going to have to completely revise its picture of modern man between 40,000 and 10,000 years ago," said Thomas Terberger, the archaeologist who discovered the hoax. "Prof Protsch's work appeared to prove that anatomically modern humans and Neanderthals had co-existed, and perhaps even had children together. This now appears to be rubbish."

The scandal only came to light when Prof Protsch was caught trying to sell his department's entire chimpanzee skull collection to the United States.

An inquiry later established that he had also passed off fake fossils as real ones and had plagiarised other scientists' work.

His discovery appeared to show that Neanderthals had spread much further north than was previously known.

But his university inquiry was told that a crucial Hamburg skull fragment, which was believed to have come from the world's oldest German, a Neanderthal known as Hahnhöfersand Man, was actually a mere 7,500 years old, according to Oxford University's radiocarbon dating unit. The unit established that other skulls had been wrongly dated too.

Another of the professor's sensational finds, "Binshof-Speyer" woman, lived in 1,300 BC and not 21,300 years ago, as he had claimed, while "Paderborn-Sande man" (dated at 27,400 BC) only died a couple of hundred years ago, in 1750.

"It's deeply embarrassing. Of course the university feels very bad about this," Professor Ulrich Brandt, who led the investigation into Prof Protsch's activities, said yesterday. "Prof Protsch refused to meet us. But we had 10 sittings with 12 witnesses.

"Their stories about him were increasingly bizarre. After a while it was hard to take it seriously. You had to laugh. It was just unbelievable. At the end of the day what he did was incredible."

During their investigation, the university discovered that Prof Protsch, 65, a flamboyant figure with a fondness for gold watches, Porsches and Cuban cigars, was unable to work his own carbon-dating machine.

Instead, after returning from Germany to America, where he did his doctorate, and taking up a professorship, he had simply made things up.

In one case he had claimed that a 50 million-year-old "half-ape" called Adapis had been found in Switzerland, an archaeological sensation. In reality, the ape had been dug up in France, where several other examples had already been found.

Prof Terberger said that he grew suspicious about the professor's work in 2001 after sending off the skull fragment to Oxford for tests.

Further tests revealed that all of the skulls dated by Prof Protsch were in reality far younger than he had claimed, prompting Prof Terberger and a British colleague, Martin Street, to write a scientific paper last year.

At the same time, German police began investigating the professor for fraud, following allegations that he had tried to sell the university's 278 chimpanzee skulls for $70,000 to a US dealer.

Why, though, had he done it?

"If you find a skull that's more than 30,000 years old it's a sensation. If you find three of them people notice you. It's good for your career," Prof Terberger said. "At the end of the day it was about ambition."

Other details of the professor's life also appeared to crumble under scrutiny. Before he disappeared from the university's campus last year, Prof Protsch told his students he had examined Hitler's and Eva Braun's bones.

He also boasted of having flats in New York, Florida and California, where, he claimed, he hung out with Arnold Schwarzenegger and Steffi Graf. Even the professor's aristocratic title, "von Zieten", appears to be bogus.

Far from being the descendant of a dashing general in the hussars, the professor was the son of a Nazi MP, Wilhelm Protsch, Der Spiegel magazine revealed last October.

The university is investigating how thousands of documents lodged in the anthropology department relating to the Nazis' gruesome scientific experiments in the 1930s were mysteriously shredded, allegedly under the professor's instructions.

They also discovered that some of the 12,000 skeletons stored in the department's "bone cellar" were missing their heads, apparently sold to friends of the professor in the US and sympathetic dentists.

Yesterday the university admitted that it should have discovered the professor's fabrications far earlier. But it pointed out that, like all public servants in Germany, the high-profile anthropologist was virtually impossible to sack, and had also proved difficult to pin down.

"He was perfect at being evasive," Prof Brandt said yesterday. "He would switch from saying 'it isn't really clear' to giving diffuse statements.

"I'm not a psychologist so I can't say why he did it. But my guess is that when he came back from the States 30 years ago he realised he wasn't up to the job of being a professor. So he started inventing things. It rapidly became a habit.'

Yesterday the professor, who lives in Mainz with his wife Angelina, didn't respond to emails from the Guardian asking him to comment on the affair. But in earlier remarks to Der Spiegel he insisted that he was the victim of an "intrigue".

"All the disputed fossils are my personal property," he told the magazine.

Missing links and planted stone age finds

Piltdown Man

The most infamous of all scientific frauds was unearthed in 1912 in a Sussex gravel pit. With its huge human-like braincase and ape-like jaw, the Piltdown Man "fossil" was named Eoanthropus dawsoni after Charles Dawson, the solicitor and amateur archaeologist who discovered it. For 40 years Piltdown Man was heralded as the missing link between humans and their primate ancestors. But in 1953 scientists concluded it was a forgery. Radiocarbon dating showed the human skull was just 600 years old, while the jawbone was that of an orang-utan. The entire package of fossil fragments found at Piltdown - which included a prehistoric cricket bat - had been planted.

The devil's archaeologist

Japanese archaeologist Shinichi Fujimura was so prolific at uncovering prehistoric artefacts he earned the nickname "God's hands". At site after site, Fujimura discovered stoneware and relics that pushed back the limits of Japan's known history. The researcher and his stone age finds drew international attention and rewrote text books. In November 2000 the spell was broken when a newspaper printed pictures of Fujimura digging holes and burying objects that he later dug up and announced as major finds. "I was tempted by the devil. I don't know how I can apologise for what I did," he said.

Piltdown Turkey

The supposed fossil of Archaeoraptor, which was to become known as the "Piltdown turkey", came to light in 1999 when National Geographic magazine published an account of its discovery. It seemed to show another missing link - this time between birds and dinosaurs. Archaeoraptor appeared to be the remains of a large feathered bird with the tail of a dinosaur. The fossil was smuggled out of China and sold to a private collector in the US for £51,000. Experts were suspicious and closer examination showed the specimen to be a "composite" - two fossils stuck together with strong glue.

David Adam