CAIRO – The DNA tests that revealed how the famed boy-king Tutankhamun most likely died solved another of ancient Egypt’s enduring mysteries – the fate of controversial Pharaoh Akhenaten’s mummy. The discovery could help fill out the picture of a fascinating era more than 3,300 years ago when Akhenaten embarked on history’s first attempt at monotheism.

During his 17-year rule, Akhenaten sought to overturn more than a millennium of Egyptian religion and art to establish the worship of a single sun god. In the end, his bold experiment failed and he was eventually succeeded by his son, the young Tutankhamun, who rolled back his initiatives and restored the old religion.

No one ever knew what became of the heretic pharaoh, whose tomb in the capital he built at Amarna was unfinished and whose name was stricken from the official list of kings.

Two years of DNA testing and CAT scans on 16 royal mummies conducted by Egypt’s Supreme Council of Antiquities, however, gave the firmest evidence to date that an unidentified mummy – known as KV55, after the number of the tomb where it was found in 1907 in Egypt’s Valley of the Kings – is Akhenaten’s.

The testing, whose results were announced last month, established that KV55 was the father of King Tut and the son of the Pharaoh Amenhotep III, a lineage that matches Akhenaten’s, according to inscriptions.

KV55 had long been assumed to be too young to be Akhenaten, who was estimated to be in his 40s at the time of his death – but the testing also established the mummy’s correct age, matching the estimates for Akhenaten.

“In the end there was just one solution for this genetic data fitting into the family tree and this showed us this must really be Akhenaten and could not be any other,” said Albert Zink, director of the Institute for Mummies and the Iceman at the European Academy in Bolzano, Italy, who worked on the project.

Now experts are planning more tests to uncover further details about Akhenaten’s royal family. The new attention could also give a push to a planned new Akhenaten museum that will showcase his mummy near Amarna, his capital midway down the Nile in what is now the province of Minya, 135 miles south of Cairo.

In one tantalizing discovery, the testing established that another unidentified mummy was Akhenaten’s sister, that he fathered Tutankhamun with her and that she appears to have died from violence with blows to her face and head.

Still elusive is Nefertiti, the chief wife of Akhenaten famed for her beauty. Egypt’s antiquities chief, Zahi Hawass, has said one of his goals is to track down her mummy.

“The Amarna period is like an unfinished play,” Hawass said at the February news conference announcing the new discoveries. “We know its beginning but have never succeeded in discovering its end.”

The discovery of Akhenaten’s remains lay to rest longtime speculation over his physical appearance. Royal statues of the time show an effeminate figure with womanly hips, elongated skull and fleshy lips – leading to speculation he suffered from any number of rare diseases that distorted his body.

But the mummy and DNA tests showed a normally shaped man without genetic conditions that might have given him both masculine and feminine features.

“It ought to dampen down some of the more dramatic interpretations,” said Barry Kemp, who has been working on the Amarna excavations since 1977. “But people do love a good story.”

What the discovery does not resolve, however, is the mystery of how Akhenaten died. Unlike Tutankhamun’s well preserved mummy, which showed he suffered from congenital defects and malaria, Akhenaten’s remains are little more than bones with no soft tissues to provide clues to his death.

In fact, the difference in preservation between his skeleton and all the other royal mummies could have been due to his different religious beliefs or animosity by those burying him.

“I think it’s another evidence that it really could be Akhenaten; he was treated differently, not in the same way as the other mummies,” said Carsten Pusch, of the Institute of Human Genetics in Tubingen, who also worked on the project.