Walking with our ancestors: human evolution in Olduvai Gorge

Walking with our ancestors: human evolution in Olduvai Gorge, Ngorongoro Conservation Area, Tanzania

Today was all about how human evolution and geology teamed up to record some of our earliest ancestors. We started with a huge delicious breaky then waited for Kimambo and Daudi to pack up camp, without our assistance. Once on the road we headed for the gate to Ngorongoro Conservation Area. We had already noticed how the plain we drove across was of a rich, red, volcanic soil. This nutrient rich soil coupled with moist micro-climate from the highlands have created a prime agricultural area and fertile forest compared to the Rift Valley floor.

Ngorongoro is a Masai word that has many meanings: first, it is the word for “bowl” because the crater looks like the Masai grinding stone bowl; second, it is another name for the tribes (Mbulu and Datogo) the Masai drove our to gain this area; and third, it is the sound that cowbells make (cows being very important features in Masai life for milk, blood, meat, and money). Originally the Serengeti was a huge area, but when the government made it a national park they wanted to remove the tribes living there. So they split it into three portions, Ngorongoro Conservation Area where Masai can live but not hunt, Serengeti National Park where no people or hunting is allowed, and Loliondo where Masai and other tribes live and hunt and where game hunting is permitted to tourists. Though the NCA and Loliondo do not have the notoriety of SNP, they are important migration grounds for animals. In fact, right now, most of the animals are migrating through Ndutu away from the Serengeti. Serengeti is also a Masai word (actually spelled Sirengeti) for “endless plain.”

Ngorongoro is a very large volcanic province of basaltic shield volcanoes. The crater is actually a huge, intact, and unfilled caldera. It formed 2 to 3 million years ago from the collapse of a large volcano that is predicted to have been of similar size to Mt Meru and Mt Kilimanjaro. There are several freshwater springs that feed into the crater and collect at Lake Magadi, enabling lush vegetation growth. The volcano was basaltic with minor trachytic lavas.

While at the gate there was a bit of a wait while Daudi worked out a mixup with our reservation number. It was fine with Melissa and I though. There was a small museum area showing the region, geology, and common animals and birds. We enjoyed it. Then a troop of baboons came to play at the gate with all the parked vehicles, looking for mischief. The alpha male walked about a foot away from me as he climbed up our truck followed by a mother baboon with her baby clinging under her belly. Baboons are so desensitized to humans they will go into open windows looking for food, and if they find nothing, they will leave a giant deuce (i.e. poop) on the seat as punishment. As funny as that sounds, the troop spotted a vehicle with an open window and one baboon was able to run off with what looked like bananas. It was hilarious watching the men run off the baboon, already in possession of its prize. It climbed right up a tree and stared down at the ruffled humans below. Silly humans.

To our delight, that was not our only wildlife exposure today. We saw so many animals! First, there was a group of Cape buffalo, or African buffalo (Syncerus caffer), right on the side of the road munching through the tree-covered crater rim. I decided to make a special animal recap post for the end of this trip since there will be so many interesting animals, so keep an eye out. We then had a vista down into the crater and saw what Daudi said were maybe black rhinos or wildebeest, its impossible to say without super zoomed binoculars. Melissa and I almost paid the steep price to drive through the crater, but Daudi convinced us we were mostly just missing black rhinos and they are rarely anywhere near the road. There are a few other other animals we might have seen in there, but we trusted Daudi’s advice. Being only 20 members strong as the final genetic offerings of black rhinos, we completely understood their distant lifestyles and let them be. Continuing forward, we also saw giraffes, Grant’s gazelles, zebras, more olive baboons, Thompson’s gazelles, wildebeests, an agama lizard, two dik-dik antelopes, numerous dung beetles, and a hyena. A bigger part of the animals was my discovery that Daudi went to university for wilderness guiding and specialized in birds! We saw so many! Little Bee-eater, Cinnamon-chested Bee-eater, Kettle Egrets, Speke’s Weaver, Helmeted Guineafowl, Pied Kingfisher, Common Ostrich, Kori Bustards, Augur Buzzards, Marabou Stork, Eastern Pale Chanting Goshawk, Ring-necked Dove, Red-eyed Dove, Red-billed Oxpeckers, Red-necked Spurfowl, and Lappet-faced Vultures. Daudi also pointed out thorny Acacia trees, Baobab trees, Amarula trees, and these massive termite mounds that littered the landscape. And this was just while driving to Oldupai Museum.

Oldupai is Masai for a type of plant native to this area. The misspelled name Olduvai comes from a German explorer. It seems there are numerous misspelled names from Masai words across all this territory. We lunched in the sun by the ranger gate and then went to meet our origins.

The museum is actually pretty small, but it is packed with information. It is divided into rooms based on both the different archeological rock units the specimens were found in and the specimen ages, a somewhat nuanced distinction at first. Oldupai Gorge preserves about two million years of human history. In 1959, Dr. Mary Leakey discovered the skull of Zinjanthropus boisei, and subsequently Homo habilis and Australopithecus, to show that three distinct forms of human ancestors co-evolved in the Oldupai basin. Potassium-Argon radiometric dating revealed ages for Zinjanthropus, Homo habilis, and Oldowan stone artifacts of 1.75 million years (Leakey et al., 1961). These discoveries ignited paleoanthrological research in Tanzania, Kenya, and Ethiopia. This work culminated in a consensus that the unusual geology and climate of the East African Rift valley created an environmentally complex and variable setting which may have driven human speciation, encephalization, and migration out of Africa (Maslin et al., 2015). Thus, highlighting the relationship between hominin history with geology (paleosols, fluvial sedimentation, tuff layers) and Milankovitch-driven climatic precession cycles on lake basin and ground water levels (Ashley et al., 2014; Habermann et al., 2016). Oldupai Gorge would have greatly resembled the Lake Manyara basin, a modern analog, situated at the rift floor. This basin provides excellent paleoanthropological and paleoenvironmental preservation due to extensive marker tuff layers separating the depositional beds. Preservation is so perfect, individual blades of fossilized grass can be identified in the uppermost surface of Bed I (Bamford et al., 2008).

After finishing the exhibits, we gathered on a vista overlooking the exposed basin where the Leakey’s excavated most of the specimens. It was pretty humbling as a human to look across the landscape holding many of the known secrets for our species. And then we went down to the shifting sands. There are two anomalous sand dunes slowly shifting across the landscape. It made me think of how the Great Plains in central US had shifting sand dunes through much of the Holocene, but here on a microscopic scale. They are very weird. Apparently they form from excess ash accumulating around a rock or some structure, until a lot of material has built up. Since the sand is volcanically derived, it has a lot of iron, making it slightly magnetic, further promoting a cohesive dune body. If you throw the sand straight up, instead of blowing away, it will clump together and fall straight down. Then a unidirectional wind slowly migrates, or shifts, the dune over time. Currently about 10 meters per year. That same wind movement creates the distinct crescent shape of the dune. And there are hundreds of dead dung beetles floating around in the pile. It was a strange encounter. Unfortunately we did not have enough time to visit Laetoli Footprints. That would have been extra special. I suppose my title is misleading since we never actually walked along the footprints. We did see all the remains and footprints replicas. I still feel tickled since this is where they mostly come from, so replica or not, my feet touched the same earth. Most of the specimens collected from Oldupai are now housed in the Dar es Salaam Museum. I can understand. Security is low here and exposure to the masses is more obtainable in Dar es Salaam.

We also viewed an active dig site for a group from Spain who found rhino bones in an ash layer. They only started three days ago. Just think what they might find! Unknown archeological riches may be found in the different beds as current interests expand the efforts from the Leakey’s. We saw Leakey Camp too. Originally Melissa and I were trying to stay there, but we never heard back from our various inquiries. We did have a neat connection with the guide who took us to the shifting sands, he knows Jackson Njau, one of the Indiana University professors we contacted during our research. James Brophy (geologist) and Jackson Njau (archeologist) provided us with an extensive field guide they have created for a summer field course they bring to Tanzania each year.

After our gawking at the museum, we picked up our Masai camp host, Lucas, and he lead us to where we were allowed to camp. Right smack in front of a kopje! Part of camping in the NCA is that we must have a Masai host. This is a Masai rule, but also for our safety. The second we stepped into the NCA Melissa and I were made aware of a single important rule: we were not allowed to ever leave camp or go walking anywhere without being safely situated inside our vehicle. This is because the NCA is where people and wildlife still coexist. And as ignorant tourists, chances were high we would become the lunch of one of those animals if not kept under strict observance. I was literally chastised for walking too far away from the truck to pee even though the area was completely open. Lions, cheetahs, and hyenas like to hide in low scrub, buffalo and wildebeests like to stampede at a moment’s notice, and there are likely a myriad of other ways we could die. I was not prepared to such confinement. I think Melissa and I both recorded less than a mile’s movement for both of the days we were here. Lucas did walk us up to the top of the kopje for the sunset while they set up camp. I think they are trying to keep us busy to not hear pleas of us wanting to provide assistance. They are so patient with us.

And yes, I said we are camped at a kopje! Much of this region, I will broadly call it the Serengeti, is a flat plain of volcanic ash burying the pre-Cambrian rocks below. The Tanzanian craton is between 2.7 to 2.4 billion years old, and is surrounded by the Mozambique Metamorphic Belt. We are over the eastern side of these metamorphic rocks, about 600-550 million years in age (Proterozoic). This suite of rocks is known as a greenstone belt, and are among the oldest in the craton, likely representing the original continental crustal mass that makes up the modern African continent. This eastern portion is largely high-grade micaceous schists (i.e., meta-schist) that formed from ancient clay-rich sediments like mudstone and shale. These meta-schists are intruded by granite bodies that are thought to have melted from the meta-schists. The granite bodies are more resistant to weathering, thus resulting in isolated hills as ash fall sufficiently covered the low-lying meta-schists. These granite hills are what are known as kopjes. Hence we are camped under the protection of melted basement rock, or erosional granite inselbergs. Neat!



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