The oldest evidence of burial customs in the Horn of Africa comes from cemeteries in Somalia dating back to 4th millennium BC. The stone implements from the Jalelo site in northern Somalia are said to be the most important link in evidence of the universality in palaeolithic times between the East and the West.

Answer this question, if possible (if impossible, reply "unanswerable"): From what millennium do the oldest cemeteries in the Horn of Africa date?
4th millennium BC