Paleontologists are inching closer to the exact spot where modern day Homo sapiens first originated, and they found help through a rather unlikely clue. The fossilized skull of a whale that lived 17 million years ago is drawing them to humanity’s origins in East Africa. Here’s how:
The whale, classified as Ziphiidae, existed at a time when warm climates brought the East African plateau considerably lower than it is today. Unlike the dry grasslands it is today, this region was then hidden under dense foliage, according to the researchers. At some point it lifted far above the sea, pushing away much of the moist winds that these jungles were dependent upon – drying the land into a savannah. For scientists, it’s really been a question of when this separation between the plateau and the Indian Ocean took place.
Our distant ancestors may have swung from trees in the East African jungles, but as the trees died out in favor of grasses, our ancestors began the transition to walking upright on two legs, suggests the new research.
“It’s more or less the story about the bipedalism,” said study researcher Henry Wichura, a postdoctoral geoscience student at University of Potsdam in Germany.
The discovery of a skull belonging to a beaked whale, ziphiidae, buried in the rock layers has now allowed scientists to pinpoint the dates when the plateau began rising – sometime in the Pliocene – between approximately 17 million and 13.5 million years ago.
The whale skull was first discovered over 50 years ago – found by fossil hunters back in 1964 is one of rediscovery. Researchers originally found the fossil in 1964, but no studies were conducted on it for another decade. Then, the skull was misplaced, hidden in a museum archive at Harvard University until 2011. Surprisingly, it was discovered in the former office of the legendary paleontologist and science educator, Stephen Jay Gould. According to the study, it was placed there for safe keeping when the school’s archives were undergoing renovations.
The skull’s provenance is a bit more important than its discoverers first imagined. It is the oldest known fossil of a beaked whale, a rather puzzling discovery if you consider that these animals are actually deep sea divers. The fossil was uncovered 460 miles (740 kilometers) inland from the modern East African coast, and at 2,100 feet above sea level.
When it was alive, Wichura’s beaked whale grew to be 23-foot-long (7 m), swimming in the Indian Ocean. One day, however, he accidentally swam into a river towards present-day Kenya, where he eventually became trapped before his death.
“We came to the idea that it used a large river system, because the whale had been found in lake sediments which are [mixed with] river sediments,” Wichura said. “So we can say that it died in a kind of river-lake environment.”
The story might sound strange – a whale in a riverbed, but crazier things have happened. There are five known species of dolphin who prefer freshwater including the tucuxi, a close relative of marine dolphins that is found exclusively in the Amazon River basin. A sixth species recently became extinct. Back in 2006, a whale got stranded in the Thames River outside London, and killer whales have been found in the Columbia River near the Pacific Northwest. With the rapidly changing sea levels, incidents of this nature may have been more common.
In order to determine the depth of the prehistoric river basin, scientists took the grade of the steepest river out of the area’s case reports, applying its relative depth to the area. Were this 17 million year old river to rise 2.5 inches per mile from the coast, then the East African plateau would be somewhere between 79 feet and 121 feet high when the whale became stranded and died. They kept the difference in height as a variable – allowing that the whale may have chosen several different routes to swim along when entering the river.
Because the plateau is approximately 2,034 feet (620 m) high, the northern part of this plateau was lifted by almost 1,925 feet (590 m) within the last 17 million years.
Somewhere around 13.5 million years ago, Wichura learned that one portion of this land mass had already begun uplifting, giving the researchers a reasonable window into when the uplift started. The researchers were even able to attribute the cause of the uplift – mantle plumes – in which heated material is released from an underwater volcano from the Earth’s mantle and presses against its crust.
Had they not rediscovered the forgotten skull, this dating would have been considerably difficult.
“With the whale, everything started,” Wichura said to Live Science.
The study is a reminder to fossil hunters – both professional and amateur alike – that very often, the precise location of a fossil can sometimes be just as valuable – if not more – than the fossil itself, when it comes to understanding the prehistoric world in full context. The discovery of a single species is hardly significant on its own, but its place in time can reveal information about an entire extinct ecosystem, or even the history of a landscape that was once very different.
“Even single specimens of organisms tell us a great deal about the history of the Earth, and they sometimes appear in surprising cases,” Brown said. “This is one such case.”
This study was published on March 16 in the journal Proceedings of the National Academy of Sciences.