8-foot-long stegodon tusk found in Pakistan

An ancient tusk unearthed in Pakistan could hold clues to the evolution of the modern elephant.

On Sunday, a group of scientists with the University of Punjab found a unique, intact stegodon tusk.

Intact tusks are rare, and this specimen should contribute to the understanding of the stegodon, a distant cousin to the modern elephant thought to have roamed the earth around 1.1 million years ago.

The tusk measures about 8 feet long and 8 inches across, say university officials. Scientists hope the tusk could help unlock some of the puzzle surrounding the evolution and lives of an extinct genus of the elephant family.

"This discovery adds to our knowledge about the evolution of the stegodon, particularly in this region," Professor Muhammad Akhtar, a scientist and the lead researcher on the trip, told AFP. "It also sheds light on what the environment was like at the time of the animal's life."

Dr. Gerrit van den Bergh, a paleontologist and stegodon expert, cautioned AFP that the tusk would need further verification.

The tusk is estimated to be 1.1 million years old, from the late Pleistocene period, which would correlate to a time period when stegodonts were still thriving, according to Dr. Bergh.

Professor Akhtar estimated the tusk's age using the uranium/lead radioactive dating technique. Like carbon dating, uranium/lead dating uses the radioactive decay of a naturally-occuring element, in this case uranium-238. By comparing the ratio of uranium-238 to its daughter-product, lead-206, scientists can calculate an object's age: the more daughter-product, the older it is. 

Stegodon fossils are not particularly unusual finds, but few bones survive more than a million years intact. "If you have a complete tusk, that's quite special – they are quite rare," Bergh told AFP.

Stegodon tusks are straighter than those of most members of the elephant family tree. Their unusual teeth, with low crowns and peaked ridges, suggest stegodonts lived on a mixed diet and lived in forested areas. Modern elephants have flatter teeth better suited for grazing. 

The species originated in Africa but quickly spread throughout Asia, indicated by the distribution of fossil data collected by the Fossilworks database. 

“They are mostly an Asian species but remains have been found further afield. Recently a molar fragment was discovered in Greece," Van der Bergh told AFP. 

Bergh has also studied stegodon fossils from islands around Asia. Findings from Flores, Indonesia, suggest a dwarf population of the elephantoid could have survived longer than its bigger ancestors.

"Because of their great potential to colonize islands, fossil elephantoids are also frequently encountered on other islands in the region," Van der Bergh wrote in the study.