Horus beheads Isis and she replaces her original head with that of a cow—an origin myth explaining the cow-horn headdress that Isis wears. Isis's maternal aspect extended to other deities as well. The Coffin Texts from the Middle Kingdom (c. 2055–1650 BCE) say the Four sons of Horus, funerary deities who were thought to protect the internal organs of the deceased, were the offspring of Isis and the elder form of Horus. In the same era, Horus was syncretized with the fertility god Min, so Isis was regarded as Min's mother. A form of Min known as Kamutef, "bull of his mother", who represented the cyclical regeneration of the gods and of kingship, was said to impregnate his mother to engender himself. Thus, Isis was also regarded as Min's consort. The same ideology of kingship may lie behind a tradition, found in a few texts, that Horus raped Isis. Amun, the foremost Egyptian deity during the Middle and New Kingdoms, also took on the role of Kamutef, and when he was in this form, Isis often acted as his consort. Apis, a bull that was worshipped as a living god at Memphis, was said to be Isis's son, fathered by a form of Osiris known as Osiris-Apis. The biological mother of each Apis bull was thus known as the "Isis cow". Isis was said to be the mother of Bastet by Ra. A story in the Westcar Papyrus from the Middle Kingdom includes Isis among a group of goddesses who serve as midwives during the delivery of three future kings. She serves a similar role in New Kingdom texts that describe the divinely ordained births of reigning pharaohs. In the Westcar Papyrus, Isis calls out the names of the three children as they are born. Barbara S. Lesko sees this story as a sign that Isis had the power to predict or influence future events, as did other deities who presided over birth, such as Shai and Renenutet. Texts from much later times call Isis "mistress of life, ruler of fate and destiny" and indicate she has control over Shai and Renenutet, just as other great deities such as Amun were said to do in earlier eras of Egyptian history. By governing these deities, Isis determined the length and quality of human lives. Goddess of kingship and protection of the kingdom Horus was equated with each living pharaoh and Osiris