The first-ever female ruler ...
... well, at least the first we'll probably ever know much about, was, I learnt today, Merneith (lots of other spellings possible) of what we call the first dynasty of the united Egypt, about 3,000BC. The clinching data about her role, according to the British Museum display (room 64), and the gallery talk speaker, is a seal found in 1988 that amounts to an early kinglist.
It runs Narmer (well-known from the famous palette, although the unification of the Two Lands is now thought to have been largely a gradual process, rather than one great war that he won, which was the story when I first read Egyptology), Djet, Merneith and Den (her son, who may have led campaigns as far afield as Palestine).
Although it is less confident than the speaker today, this site contains most of the information known about Merneith. Some other, non-ruling queens from the period are also known, at least by name.
I learnt that the first palettes were used to grind eye makeup for the statues of the gods, but they gradually became both more elaborate and purely ritual items. One in the gallery shows what may be an early step in the direction of hieroglyphs, with a picture of a shrine beside one of a two-headed bull (known to be an early god), which probably identifies it.
Generally, however, from our current knowledge hierogylphs emerge very suddenly, but already in a highly sophisticated form, about 3,200BC (although this date is currently the subject of fervent debate), what we call the start of early dynastical Egypt. This indicates there must have been several centuries of gradual development in a form that has not survived.
The movement from the "early dynastic" period into the Old Kingdom comes with the sudden explosion of the use of stone, particularly for building, and the pyramids. It was only during the First Dynasty that Egypt practiced human sacrifice, with the king's servants being killed to serve their master in the afterlife. The speaker suggested this died out fast because the next king found he lacked vital skills in his court as a result of the practice.