A 17 million year old whale fossil, discovered more than 450 miles inland at at an elevation of more than 2000 feet above sea level provides important clues about the uplift of the Great Rift Valley of East Africa.

The change in the areas elevation and the changes in climate that came with it are thought to have been a catalyst to the evolution of primates from tree dwellers to upright walking animals that lived on the plains.

For decades the timeline and changes that occurred during the uplift have been a source of debate. The discovery of the beaked whale in, what is now, a harsh desert region, helps provide important clues according to vertebrate paleontologist Louis L. Jacobs, Southern Methodist University in Dallas.

No other whale has been found so far inland in Africa. When it was still alive, the whale would have been swimming upriver with a low gradient of 78 to 120 feet for a distance of 370 to 550 miles, according to Jacobs. The discovery provides an important clue about when the elevation, or uplift of East Africa from sea level to its current elevations began.

“The whale was stranded up river at a time when east Africa was at sea level and was covered with forest and jungle. 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,” said Jacobs, in a statement.

Jacobs is a co-author of a study, “A 17 million-year-old whale constrains onset of uplift and climate change in East Africa,” published in the Proceedings of the National Academy of Sciences.

The fossil, identified as Turkana ziphiid was not a river dwelling animal but had made it’s way upriver from the open ocean as whales will occasionally do today.

Ziphiids, the ancestors of the fossilized animals, are still a top predator and are considered one of the ocean’s top predators. The beaked whales dive deeper than any other known mammals, plunging to depths approaching 10,000 feet to feed.

Most whale fossils are found in marine rocks and it is unusual to find such a fossil in river deposits.

The ancient river, the Anza, flowed southeastward to the Indian Ocean. The whale, according to the researchers, swam into the river and was unable to change course, proceeding inland for hundreds of miles.

“You don’t usually find whales so far inland. Many of the known beaked whale fossils are dredged by fishermen from the bottom of the sea,” said Jacobs.

It is normally very difficult to determine the ancient elevation of land, but the inland discovery of marine species is a good clue. The only other evidence for the uplift in East Africa comes from the discovery of a lava flow.

The discovery of the whale fossil was originally made in the Turkana region of northwest Kenya in 1964. J.G. Mead, who made the find, recently retired from the Smithsonian Institution but was an undergraduate student at Yale University at the time.

The whale the fossil came from was estimated to have been 23 feet long. The portion found, however, was only the 2.6 foot long, 1.8 foot wide beak portion of the skull.

The whale fossil went missing for many years. Jacobs, who was at one time head of the Division of Paleontology for the National Museums of Kenya, spent 30 years looking for it before finally rediscovering it at Harvard University and returning it to the Kenya’s National Museum.