Celestial guidance. This ancient carving may have been used to time pregnancies.

Celestial Fertility Guide

The purpose of one of the oldest objets d'art may finally be solved. The 32,000- to 38,000-year-old carving on a sliver of mammoth tusk represents the constellation Orion and could have been used as a fertility guide, says a German archaeologist.

The pocket-sized tablet was found in 1979 buried within the collapsed Geißenklòsterle cave in southern Germany. Researchers soon offered several possible identities for the figure carved on its surface, including the hunter Orion. But they were not able to reach a definitive conclusion.

Now suspecting that the key to the puzzle might be that Orion looked different when the figure was made, Michael Rappenglück of the Institute for Interdisciplinary Studies in Gilching-Geisenbrunn, Germany, has used a computer program to show that the figure closely tracks what the constellation would have looked like 32,000 years ago. In particular, he says, one of Orion's stars (phi2 Ori) has shifted from the top of the hunter's head, where it appears in the figure, into the neck, where we see it today. He also offers an explanation of how ancient people used the 87-odd notches on the opposite face of the tablet. From the perspective of the cave about 32,000 years ago, Rappenglück calculates that Orion's brightest star, Betelgeuse, would have been invisible beyond the night horizon for 3 months of each year, roughly equivalent to 87 nights. Rappenglück speculates that people might have used the tablet to keep track of days during this period because children conceived then would be born during winter, a slow time for paleolithic women, rather than spring to fall, when migration and food-gathering kept them on their feet. Rappenglück's paper will appear in the August issue of the Proceedings of the European Society for Astronomy and Culture.

"We can never be 100% sure" about such ancient objects, but the Orion hypothesis seems plausible, says astronomer Juan Belmonte of the Institute of Astrophysics in the Canary Islands, a specialist in prehistoric astronomical systems. If Rappenglück is right, the tusk carving would be the earliest known star chart. It is some 16,000 years older than a possible star chart on the walls of France's Lascaux cave.