Early Indians: The Story of Our Ancestors and Where We Came From

by Tony Joseph

Geologists in the 1960s and 1970s discovered a way to figure out the chronology of global climate fluctuations by drilling the deep sea to get sedimentary cores and then looking at the oxygen isotope data that these contained at different depths. High levels of Oxygen-18 represent cold, glacial periods and low levels of Oxygen-18 represent warmer, wetter periods. Based on this, we can now look back at the climatic history of the world for the past many millions of years, which has been divided into periods called Marine Isotope Stages (MIS). Currently we are in MIS 1, a warm, wetter period that began about 14,000 years ago and is still continuing. Odd-numbered MIS stages are all warm and wet, while even-numbered MIS stages denote cold and dry glacial periods.