Racism.
The first plow appeared in Africa. Writing appeared everywhere, including Africa. Simple tabby weaving by hand also occurred pretty much everywhere, including Africa. Africans used the wheel long before a lot of other people did. They also watched the stars a lot more than people do today, and developed a calendar from it.
Laws were simple. Basically tribal elders were the law.
Measurements were based on how far a man typically walked in a day. There was no need for anything else.
Math is not created. It simply exists.
There was no need for a sewer or for drilling a well.
Irrigation was invented in Africa, using the Nile river as it's source headwaters.
Yes. That's also agriculture.
There was little need to build a road. They just happened wherever people traveled. Just a worn track, really.
There being no sea to worry about most of the time, there was no need for a sea vessel.
They did domesticate animals.
The did exploit underground resources, typically keeping accurate memory on where underground water could be located.
Even a stick was used as a mechanical device. Sometime you should look up what a lever is.