Number 118 (Story #4), March 12, 1993 by Phillip F. Schewe and Ben Stein ICE-AGE CAVE ART can be dated much more carefully now with accelerator mass spectrometry (AMS) techniques. For example, three painted bison on the ceiling of the Altamira Cave in northern Spain were thought to be done at the same time, about 14,000 years ago. French and Spanish scientists have recently shown that the three were actually painted centuries apart, 13,570, 13,940, and 14,330 years ago. The greater precision in this case comes from the use of AMS which, instead of just sampling current carbon-14 radioactivity, directly compares the carbon isotopes present in the sample by ionizing, accelerating, and sorting them. (New Scientist, 27 Feb. 1993.)