A whale fossil dated to 17 million years ago is pushing back the date investigators believe a large tectonic shift took place in eastern Africa.

This event resulted in an uplift of the ground of Africa, and drove aridification, drying out the region. These conditions are believed to have played a major role in the evolution of human ancestors. However, details of this geological event have been difficult to record, as the initial altitude of the ground and the date when the shift began were both uncertain.

A beaked whale fossil from the family Ziphiidae was discovered in a location placed 460 miles inland of Africa's current coast, suggesting the species was able to travel at least that far at the time the whale lived. The animal was likely swimming along a river when the animal perished, slowly becoming fossilized over time. At the time the whale perished in the river, much of the ground in east Africa was near sea level, leading to moist conditions that covered the region in jungles and forests.

"As that part of the continent rose up, that caused the climate to become drier and drier. So over millions of years, forest gave way to grasslands. Primates evolved to adapt to grasslands and dry country. And that's when -- in human evolution -- the primates started to walk upright," Louis L. Jacobs, a vertebrate paleontologist from Southern Methodist University, said.

Thought to be 17 million years old, this Turkana ziphiid is believed to be the most accurately dated beaked whale fossil in the world.

The ancient whale likely lived in the Indian Ocean and became disorientated, swimming in a northwest direction up the Anza River. The creature may have been unable to turn around in the waterway, swimming inland until it perished in fluvial sediments.

Due to the topology of the land, this artifact provides a marker of sea level in the region at the time the animal lived. The fossil was first discovered in 1964, and was missing for decades before it was recovered at Harvard University in 2011.

Ziphiids hold the record for diving deeper under the water than any other air-breathing animal. The species lives in the open ocean, as did their distant ancestors, and are among the world's top marine predators.

Discovery of the ancient whale fossil and analysis of how it could assist in dating the uplift in eastern Africa was profiled in the journal Proceedings of the National Academy of Sciences of the United States of America (PNAS).

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