Many educated people know that the genetic material is DNA and is located in the nucleus of the cell. Less commonly known is that bodies in the cell known as mitochondria also have DNA. Mitochondrial DNA characteristics are such that it is a useful tool for studying relationships between species. This DNA also is used as a molecular clock. The theory is that changes—mutations—in mitochondrial DNA for any group of organisms arise at a steady rate. The rate theoretically can be calibrated for a group by events in the fossil record. Once the rate is known, the number of differences between members of the group can be used to determine when the members became separated.
Such studies recently were carried out on wolves, with the result that
a group of wolves from northern India apparently have been separated from other wolves
for about 800,000 years, and wolves from the plains of India about 400,000 years. In
comparison, our wolves of northern Eurasia and North America are practically puppies,
having separated from others only about 150,000 years ago.
Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.
Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.