Washington, June 12 : A genetic study has revealed that the woolly mammoth was not one large homogenous group and had split into two groups, with one of the groups dying out 45,000 years ago, which further suggests that the animals went extinct because of climate change and disease, not human hunting.
The study was carried out by Penn State University genomicists Webb Miller and Stephan C. Schuster, using the Roche/454 Life Sciences Genome Sequencer 20 System, which was used to sequence mammoth mitochondrial DNA from the hair of woolly mammoths.
"The population was split into two groups, then one of the groups died out 45,000 years ago, long before the first humans began to appear in the region," said Stephan C. Schuster, associate professor of biochemistry and molecular biology at Penn State University and a leader of the research team.
"This discovery is particularly interesting because it rules out human hunting as a contributing factor, leaving climate change and disease as the most probable causes of extinction," he added.
The scientists analyzed the genes in hair obtained from individual woolly mammoths - an extinct species of elephant adapted to living in the cold environment of the northern hemisphere.
The bodies of these mammoths were found throughout a wide swathe of northern Siberia. Their dates of death span roughly 47,000 years, ranging from about 13,000 years ago to about 60,000 years ago.
Whereas studies before this research had analyzed only short segments of the DNA of extinct species, this new study generated and compared 18 complete genomes of the extinct woolly mammoth using mitochondrial DNA, an important material for studying ancient genes.
Data from this study will enable testing of the new hypothesis presented by the team, that there were two groups of woolly mammoth - a concept that previously had not been recognized from studies of the fossil record.