Winter count

Pastoralists and hunters know leather. They also write on leather. Observe: the Lakota Winter Count, from 1786. Based on a 2007 book so, maybe more such calendars exist or might be found in some cave somewhere.

This looks for all the world like Aztec pictography, before the rebus they came to use. The linguistics tell us that Nahua tribes came from buffalo regions, along the Front Range down to Texas. So I expect the genre dates back at least to the AD 800s, in reaction to the drought. A script-of-their-own may explain how, although assuredly exposed to the Maya Hieroglyphic, the postToltec Nahua Altiplano did not adopt this foreign script or even abandoned it.

From El Norte - and conversely - this might further explain how we don't find the Lakota using "their own" calendar until they moved into those Plains (they came from the Lakes). Taken from the locals, methinks; as today, newbies need a simple manual.

I don't know if any pictographic system ever came into use south of Sahara. I do know that subSaharans (and Saharan "Berbers") took to (alphabetic) writing as soon as they found out that writing was possible. I also do not know if we might find similar Winter-Count systems in some tundra in Ice Age Siberia...!