TOW (& Answer)...

This week’s question was what calendar system did the Borana people of southern Ethiopia and northern Kenya use?  They used a system based on the conjunction of seven selected stars with various phases of the moon.  The Turkana site, built to help make the necessary sightings in around 300 BC, would indeed correctly line up with the correct star positions at that time.  

Read more about the system on p. 14-15 of Volume 3 of the History of Science.  The work was edited by Dr. Peter Whitfield and published in 2003 by Grolier.