A prehistoric circle made almost entirely of mammoth bones has been found in Russia. The “bonehenge” was built near the peak of the last glacial period, but it isn’t clear why.

Stone Age people made many bone circles in eastern Europe and northern Asia in the last 22,000 years. One of the best-known sites is Kostenki 11, south of Voronezh in Russia. Two circles of mammoth bones were found there in 1951 and 1970, and have been studied …