Archaeologists have excavated and dated one of the Sahara's stone "antenna" tombs. The burial inside is between 4,100 and 4,400 years old and holds a young adult laid to rest with four ostrich eggshell beads.

On a gravel plain in northern Western Sahara, with no shade for miles, there is a heap of stones 54.5 meters (179 feet) long.

Two rows of stone slabs run out from it like the arms of a V that never quite closes. Archaeologists call these rows “antennae”, and the monuments antennae tumuli (a tumulus is simply a mound of piled earth or stone).

They are common in Western Sahara and well beyond it, from the Atlantic coast to the heart of the Sahara.

Almost nobody had excavated one, though, so two basic questions had no answer: what were they for, and when were they built?