It has long been known that the practice of mummification of the dead in ancient Egypt — fundamental to that civilization's belief in eternal life — was old, but only now are researchers unwrapping the mystery of just how long ago it began.

Researchers on Wednesday said a form of mummification was being carried out there more than 6,000 years ago, much earlier than previously thought. They said embalming substances contained in funerary textiles from the oldest-known Egyptian cemeteries showed mummy-making from as early as about 4300 B.C.

The embalming agents were infused into the linen used to wrap the corpse to provide an antibacterial and protective barrier. It was not as elaborate as the process used much later on the bodies of powerful pharaohs and other elites as well as many ordinary Egyptians, but came more than 1,500 years earlier than Egyptian mummification had been thought to have started.