An ancient Egyptian mummy whose identity had baffled experts since it was found in a mass tomb in 1907 has been determined, through a comparison of facial X-rays of royal mummies, to be that of King Tutankhamen's half-brother, Smenkhare.

Until the new analysis, an argument had persisted among Egyptologists on as elementary a point as whether the slightly built, badly preserved mummy was male or female.

The identification, carried out by James E. Harris and Brian Ingalls, orthodontists at the University of Michigan, relied on an X-ray method developed by dentists to see how a patient's facial bones change shape in response to orthodontic treatment. Harris, an authority on the X-ray study of Egyptian mummies, converted the mystery mummy's X-ray images into a form that a computer could measure and compare with similar data from dozens of other royal mummies.

Harris' research on mummies and living families has shown that measurable similarities in facial bones are inherited in fairly predictable ways through family lineages. The computer analysis showed the mystery mummy to resemble Tutankhamen most closely.

Hieroglyphic records had said that Smenkhare served as coregent of Amenhotep IV (also known as Akhenaten). Sculptures and other funerary art depicting Tut's family showed Smenkhare as a slight, effeminate man. Putting all the evidence together, Harris concluded the mummy that many claimed was a woman was Smenkhare.