Recent archaeology has shown the Garamentes from being far more than Herodotus' description of a tribe of numerous barbarians who were good at raising cattle; indeed, they became the Sahara's first culture to develop an urban civilization absent a perennial river – by 150 BCE, their capitol, Gerna (the modern Jarma Oasis) had a population or perhaps 4000, with another 6000 living in the immediate vicinity. Eight more major towns and numerous smaller settlements dotted their realm, and a decidedly city-based culture developed to exploit transiting caravans. According to some estimates, over 50,000 of their pyramidical stone tombs dot the landscape of their former territory.
Weird Historical Sidenote: For a glimpse into what the territory of the Garamedes looks like nowadays, check out this guy's photologue of a trip to Tassili National Park in Algeria. See if you can spot the petrified elephant.
Their elaborate tunnel system made the Garamedes overly reliant upon slaves, which led to the old conquer-or-perish motif that we see played out so often through history. They warred for control of trade (and for profit) with the kingdoms surrounding them, be they Nubian, Egyptian, Carthaginian, Greek, or Roman. These latter sent several punitive expeditions into the lands of the Garamedes, but the desert proved unconquerable; finally, the Romans gave up and signed a lasting commercial and military agreement with them at the end of the 1st century CE."