But it demolishes the idea that it could never happen, Gill says. Climatologists have since corroborated the pattern with computer models and are trying to find the force controlling the High s swings. Recent research on lakes within Maya territory lend further support to the drought hypothesis. Geologists Mark Brenner and David Hodell of the University of Florida studied cores taken from lakes in the Maya lowlands to learn about ancient climate conditions. Water entering the lake typically contains equal amounts of two isotopes of oxygen.
Isotopes are atoms which have the same number of protons but different numbers of neutrons.
In dry years, more of the lighter form, O16, evaporates from the lake than the O18. In those years, animals incorporate perceptibly more O18 into their shells. The scientists found that the shells of microscopic lake crustaceans called ostracods roughly dating back to the same dates of the three periods of the Maya collapse contained unusually high amounts of O18. Mineral records in the core samples echoed these results perfectly. The lakes waters are always saturated with a soft mineral called gypsum.