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17-Million-Year-Old Whale Fossil Provides Hints for East Africa’s Puzzling Uplift

17 million year old whale

Image credit: A 17-million-year-old whale fossil stranded far inland in Kenya now sheds light on the timing and starting elevation of East Africa’s puzzling tectonic uplift / Southern Methodist University

The East African Plateau is located nearly 1,000 meters higher than sea level, however, back to millions years ago, this region was actually underwater. Not long ago, based on the study on a prehistoric whale fossil discovered at such high elevations, researchers have found that the East African Plateau started to rise above sea level around 17 million years ago, almost the same time when highly variable climate and drier conditions started to give rise to primate evolution, including that of human being. These newest findings have been made public in the recent edition of Proceedings of the National Academy of Sciences.

It was in 1964 that the fossilized skull of a deep-diving, open-ocean-living whale was found at an elevation of 620 meters in the Open Pit Turtle Mine of Williams’ Flat Loperot in West Turkana, Kenya, which was 740 kilometers inland from the Indian Ocean coastline. At present, this region is a much harsh desert (a photo presented below showing the excavation site). The 17-million-year-old fossil fell into the catalogue to the oldest beaked whale in the family of Ziphiidae, which was the only stranded whale discovered up to now inland on the African continent. It went missing from the National Museums of Kenya some years later, but reappeared at Harvard in 2011 three decades afterwards.

excavationNow, Henry Wichura from University of Potsdam and his international team, based on their examination of the newly resurfaced whale by using decades’ old field notes and phylogenetic analyses, together with 3D and CT scans, have found that this 7-meter-long beaked whale probably swam eastward from the Indian Ocean along the Anza River, the drainage system at the time. When it possibly failed to change its course, it had to swim towards inland covering the distance of 600 to 900 kilometers. In the end, it became stranded at an elevation slightly above sea level, something like 24 to 37 meters.

As Louis Jacobs, the study co-author from Southern Methodist University said, when the whale was stranded up river, East Africa was still at sea level, being covered with forest and jungle. As early as 17 million years ago, East Africa was heavily vegetated with low elevation, high rainfall and humidity. It remained unchanged until activity in Earth’s mantle forced the region to rise up to several hundred meters; of course    the whale’s fossils were up as well. According to the previous study on mantle plumes, it demonstrated that the uplift of the East African Plateau had occurred 13.5 million years ago, so at present scientists have ultimately bookended the onset of uplift.

Such tectonics had caused increased arid and open habitats. In Jacobs’s opinion, the rising of that part of the continent resulted in the climate turning drier and drier. So during the incredibly long period of millions years, forest had to give way to grasslands. Following this trend, primates evolved to get used to grasslands and dry country. That was the time when the primates began to walk upright, similar to human evolution

Talking of this phenomenon, Wichura said, it is almost s more the story closely linked with the bipedalism.

 

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Images: Southern Methodist University (top), James G. Mead (middle), H. Wichura et al., PNAS 2015 (bottom)

Source: SMU Research, EurekAlert!, and live science.

Journal reference: Wichura, Henry, et al. “A 17-My-old whale constrains onset of uplift and climate change in east Africa.” Proceedings of the National Academy of Sciences(2015): 201421502.

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