Cryptic (geology)
The Cryptic era is an informal term for the earliest geologic evolution of the Earth and Moon. It is the oldest (informal) era of the Hadean eon, and it is commonly accepted to have begun close to 4533 million (about 4.533 billion) years ago when the Earth and Moon formed. No samples exist to date the transition between the Cryptic era and the following Basin Groups era for the Moon (see also Pre-Nectarian), though sometimes it is stated that this era ended 4150 million years ago for one or both of these bodies. Neither this time period, nor any other Hadean subdivision, has been officially recognized by the International Commission on Stratigraphy.
Hadendoa
The southern Beja were part of the Christian kingdom of Axum during the sixth to fourteenth centuries.
In the fifteenth century, Axum fell to the Islamization of the Sudan region, and although the Beja were never entirely subjugated, they were absorbed into Islam via marriages and trade contracts. In the seventeenth century, some of the Beja expanded southward, conquering better pastures. These became the Hadendoa, who by the eighteenth century were the dominant people of eastern Sudan, and always at war with the Bisharin tribe.