Ancient cultures made mummies for religious reasons, according to the British Museum. The Egyptians began mummifying their dead around 3500 B.C. but took almost a thousand years to perfect their technique. The earliest completely preserved Egyptian mummies were created around 2400 BC. These are called anthropogenic mummies because they were intentionally created. The British Museum states that many older corpses were naturally preserved by burial in hot, dry sand pits.
Dehydration was the key to ancient Egyptian mummification, according to About.com expert N.S. Gill. Inspired by the natural mummies preserved in sandy graves, the Egyptians learned that removing the internal organs was vital to preserving the rest of a corpse. After removing the organs, mummifiers rinsed the thoracic and abdominal cavities with wine and spices. According to Encyclopedia Smithsonian, the heart was not removed because the Egyptians believed it contained the essence and intelligence of the person and needed to remain whole for use in the afterlife.
Each of the internal organs was carefully excised, dehydrated for 40 days and wrapped in cloth. Then they were reinserted into the mummy or packed into earthenware jars and entombed next to the body.
After processing the internal organs, mummifiers bound the dead body in linen and decorated it with charms and talismans to ward off evil forces and unhappiness in the next life. The final step in the mummification process was a resin bath. The dried resin shell made the mummy impervious to ambient moisture.