17 December 2015

17. Hominid Sites of Lake Turkana

Nariokotome Boy
National Museum of Kenya
Location: Marsabit & Turkana, Kenya
Formation: Several, most notably the Koobi Fora Formation
Age: Pliocene-Pleistocene (4-2 Ma)

If the story of climate change through the Cenozoic is one of cooling and drying, the principle drama that has been played out in terms of environment is the interplay between forests and grasslands.  Both because of the number of lagerstätten there and the amount of research that has been focused them, the stage on which this drama is often set is North America.  However, places like the steppes of Central Asia and the pampas of South America tell much the same story.  So too do the savannahs of Africa, and these have been the subject of a great deal of study because they factor prominently in our own evolutionary story.  Like much of the world, Africa saw its forests give way to open environments during the Miocene, while at the same the continent began to fracture along the Great Rift Valley as the Horn of Africa began to move eastward.  The wide array of scattered environments, it has been argued, were the impetus for our earliest ancestors to leave the trees and begin walking upright (though, like almost every hypothesis in the subdiscipline of paleoenthropology, this is by no means universally accepted).  Regardless of what originally drove a particular group of apes to evolve an erect posture, by the latest Miocene and into the following epochs, the Pliocene and Pleistocene, hominins - the subfamily of Primates to which we belong - had begun to diversify into a variety of forms.  Sites along the Kenyan shorelines of Lake Turkana preserve an especially high concentration of hominin fossils, from the enigmatic Kenyanthropus, to Australopithecus (best known as the genus to which Lucy belonged, and also well known from sites in Ethiopia and South Africa), to Paranthropus (easily the most bizarre branch of the hominin tree, with enormous and robust skulls that isotopic analyses have suggested were adapted to a diet of bamboo), to members of our own genus, Homo.  The most spectacular Turkana fossil from this last category is the so-called Nariokotome Boy, a specimen assigned variously to H. erectus and H. ergaster.  The nearly complete skeleton, found on the western shore of the lake, is not only spectacular in and of itself, but is one of the best sources of information available about our own branch of the hominin tree.  The oldest rocks along Lake Turkana date to a time when the entirety of human evolution had taken place in Africa.  By the time Nariokotome Boy was alive, though, members of our genus had begun to spread across the rest of the world, where they would encounter Pleistocene ecosystems that would form the basis of some of the Cenozoic's most stunning lagerstätten and in which they would, in many cases, figure prominently.

Visit: A series of national parks surround Lake Turkana, many designated as World Heritage Sites.
Fossils: Fossil material from throughout the country is reposited in Nairobi's National Museum, but having never been, I can't vouch for how much Turkana material is on display.
Is there a relevant book full of gorgeous fossil photos that I can gift to a paleontologically-minded friend?: No, though several books focusing on human evolution are available.

This post is part of my 2015 Paleontology Advent Calendar, a series of vignettes on lagerstätten - sites of exceptional fossil preservation - that document changes in climate and environments through the Cenozoic.  You can see the other posts here.

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