This particular sea urchin was found in the Mali desert/West Africa. It measures 14 x 29 mm and weighs 20 grams. It has a tapered (man-made) perforation measuring 7 mm at the flat end and 4 mm at its convex/domed obverse. As to your question when these were used as spindle whorls - there is no specific time frame. Often spinners used objects that were easily obtainable and which offered themselves to be used as a spindle whorl, due to their respective weights and shapes. These objects could be seeds, beads, shells, echionids etc. It is known that spinners in Scotland and in Ireland (and perhaps elsewhere as well) did use a small potato, when nothing else was at hand.

Evelyn