We all are conversant with Yoruba tradition. What do you say when a king passes on to great beyond? in Yoruba tradition, its a taboo to say to someone, "the king is dead." You rather say "Oba w'aja" that is, the king has exit into upper chamber.

Aja is Yoruba for "storey- building" or "the roof". Now look at it, is it just a vain word that the ancient says to border us with their traditions or it is another tell-tale disguise of awareness of king being mummified? No Yoruba king has been buried in a roof chamber in spite of the implication of that classic tradition.

The practice in ancient Egypt is such that a dead king is embalmed or buried in a mummy. This is then taken to the pyramid for final burial or internment. The pyramids of Egypt were build for this purpose, to house the deceased king in one of the chambers that forms the pyramid.

Wikipedia have this to say "There are 138 pyramids discovered in Egypt as of 2008.[1][2] Most were built as tombs for the country's Pharaohs and their consorts during the Old and Middle Kingdom periods.

"The earliest known Egyptian pyramids are found at Saqqara, northwest of Memphis. The earliest among these is the Pyramid of Djoser (constructed 2630 BCE–2611 BCE) which was built during the third dynasty. This pyramid and its surrounding complex were designed by the architect Imhotep, and are generally considered to be the world's oldest monumental structures constructed of dressed masonry.[6] The estimate of the number of workers to build the pyramids range from a few thousand, twenty thousand, and up to 100,000."

The point is, the tradition that has come to Yoruba land as 'the deceased king tradition' has a touch of pyramid interment. Considering the population needed for pyramid building, its not strange that slavery was ingrained in ancient Egypt and this condition can really spring freedom fighters or displace sojourners.