Ancient trees suggest Genghis Khan's success was built on grass

Scientists have discovered an explanation for the phenomenal success of Genghis Khan in a most unlikely place - tree trunks.

Amy Hessl of West Virginia University and Neil Pederson of Columbia University in New York conducted a study on a stand of millennium-old Siberian pine trees growing in cracks on a lava flow in northern Mongolia.

Their team cut cross sections from the trunks of dead trees and took thin, chopstick-sized cores from living ones for comparison. The rings in the samples revealed a period of unusually warm and rainy weather between the years 1211 and 1225, coinciding precisely with the meteoric rise of Khan.

"Trees are wonderful natural archives of environmental history" Hessl told the Sunday Morning Post.

"The trees we studied can live for over a thousand years and they are extremely sensitive to changes in soil moisture. The changes create variability in the size of their annual rings and this tells us a lot about past climate conditions."

The mild temperatures and plentiful rain would have caused Central Asia's usually dry, rocky steppes to sprout a luxuriant carpet of grass. Hessl said this sudden profusion contributed to Khan's success.