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Lake Natron is a salt lake located in northern Tanzania in Africa’s Great Rift Valley, close to the Kenyan border. This shallow lake is less than 10 feet deep with a variable width that depends on its water level. The water level varies significantly between rainy and dry seasons.

tanzania1As water evaporates during the dry season, salinity levels increase promoting growth of salt-loving microorganisms. These salt-loving organisms include cyanobacteria which use photosynthesis as plants do to produce energy. Red pigment in the cyanobacteria produces the deep reds of the open water and the orange hues of the shallows of the lake. These colors are characteristic of lakes with very high evaporation rates. In addition, the alkali salt crust on the surface of the lake is often colored red or pink by the cyanobacteria.

Lake Natron is the only breeding area for the 2.5 million endangered Lesser Flamingoes that live in the valley. As salinity and cyanobacteria increase, the flamingoes flock along saline lakes in the region to feed on Spirulina (a blue-green algae with red pigments). However, Lake Natron is the only breeding location for Lesser Flamingoes because its caustic environment is a barrier against predators trying to reach their nests.The tanzania2temperatures in the mud can reach 50 degrees C (120 degrees F), and depending on rainfall, the alkalinity can reach a pH of 9 to 10.5 (similar to ammonia). Amazingly, an endemic species of fish, the alkaline tilapia, also thrives at the periphery of the hot spring inlets in these ordinarily inhospitable waters.

We had an ornithologist with us who explained that flamingoes actually originated in East Africa in this area. Flamingoes were imported to North Africa and the Romans imported them to raise them for their tongues as a delicacy…..hmmm. Spain imported flamingoes and then the US imported flamingoes from Spain to Florida, so our flamingoes actually originated in Africa. The only ones that did not are the pink plastic flamingoes we see in yards in Kentucky and rural Maryland. Anyway, they were really beautiful, especially as large flocks flying off to Ngorongoro right after sunset to feed.

The area around Lake Natron turns out to be exactly like the lake my son Tim and I visited a couple of years ago where we saw soda ash being mined at Lake Magadi. The soda ash mined at Lake Magadi is Kenya’s most valuable mineral export.

Because of threats to the salinity balance from projected logging in Natron watersheds, a planned hydroelectric power plant, and proposed development of a soda ash plant at Lake Natron, Tanzania named the Lake Natron Basin to the Ramsar List of Wetlands of International Importance on July 4, 2001. Destruction of this breeding site would be devastating to the Lesser Flamingo population.

The Ngare Sero Tented Camp was developed in 2004 around a recently discovered spring on private land leased from the Maasai in the sparsely inhabited northern border of Tanzania. This small comfortable camp is an attractive location for birders to view the flamingoes of Lake tanzania3Natron and other bird species and animals attracted to the spring waters. In 2006, a Maasai herder tending the small herd of camels at the camp came across footprints in the volcanic ash about a 10 minute drive from the camp.Preliminary indications suggested that these prints were old enough to generate scientific interest. The first scientific evaluation of the prints occurred in August 2009 when a small group of scientists headed by Dr. Cindy Liutkus excavated and mapped the visible prints and uncovered several more.

Known fossil hominin footprint sites are extremely rare and range widely in age and location from about 350,000 years in Europe (1) to the most famous track dated to 3.6 million years in Tanzania (2). Footprints provide important information about the biomechanics and behavior of our bipedal ancestors (3-6) while clues about paleoenvironments, paleoclimate, and preservation mechanisms can be determined from studies of the geology surrounding footprint sites (5, 7-9).

There was lots of game around, including many wildebeest, zebra, giraffes, jackals, some oryx. I heard hyenas near the tent but did not see any. There were no large predators because the Maasai keep them out to protect their cattle. Lots of birds also, especially around the camp which was around a clear spring that created a small lake.

The camp was about a 10 min drive from the footprint site. The whole place is in the shadow of a large volcano, Oldoinyo Lengai, one of two active volcanoes in Africa. It was quite beautiful and the landscape had all kinds of large volcanic rocks that had been spewed out by the volcano.

tanzania4“Ol Doinyo Lengai” means “Mountain of God” in the Maasai language. It is unique among active volcanoes because it produces a very rare type of volcanic carbonatite. Most lavas are rich in silicate minerals but the lava of Oldoinyo Lengai is rich in the rare sodium and potassium carbonates, nyerereite and gregoryite. This unusual composition produces lava erupted at relatively low temperatures (approximately 500-600 degrees C). Interestingly, this temperature is so low that the molten lava appears black in sunlight rather than the red glow associated with most lavas. It is also much more fluid than silicate lavas. The unusual combination of sodium and potassium carbonate minerals in lava formed by Oldoinyo Lengai is susceptible to rapid weathering and rapidly turns from black to grey in color creating a unique volcanic landscape. The chemical makeup of the lava has been compared to dish soap.

Volcanic activity in Oldoinyo Lengai caused daily earth tremors in Kenya and Tanzania beginning on July 12, 2007, and culminate in an eruption on September 4, 2007, which sent a plume of ash and steam 18 kilometers downwind and covered the north and west flanks in fresh lava flows. The eruption continued intermittently until late August 2008. Lava emission appears to have resumed from two vents in the floor of the new crater.

tanzania5The footprint site was located in the shadow of this active volcano, in the middle of a windswept area intermittently inundated by floodwaters. The impressions in the volcanic ash are very well preserved with frequent exquisite detail; volcanic ash mixed with water makes cement. Rains often accompany a volcanic eruption so maybe that was the source of water. Right next to the ash was a lava flow so it may very well be that there are more prints under the old flow. The lava actually had large rocks that had been shot out of the volcano and made a still visible splash as they landed. The rocks (called pyroclasts) were a little bit elongated because they stretched and cooled as they were shot out of the volcano. Very interesting indeed.

tanzania6There were about 25 prints when we arrived, heading in a direction away from the volcano. There were only 6 of us, including 2 Tanzanians from the Department of Antiquities, so the excavation and documentation kept us quite busy. We uncovered over 30 more prints for a total of 58 (I found about 8 or 9 myself), many of them in excellent shape. We had to shovel first gently, then brush, then chip the layer of ancient sediment above the ash gently to find prints. It was thrilling to uncover a curve that turned out to be a toe or heel. There were at least 3 individuals, probably 2 men and a woman. The woman’s track was 20 meters long, amazing (they almost named her Susanna after my daughter but will probably give her a Maasai name); I actually uncovered 6 of these. One man had about a size 13 or 14 foot and a stride 6 inches longer than mine so he must have been 6’3″ or so, very unusual because the humans of that era were thought to be shorter, about 5’6″ or so. The other man (presumably) seems to have been close to 6’0″ with about a size 10 foot. We measured each print, all the stride lengths, and charted and photographed them. The tracks appear to go right under a sand dune so there are probably many more still there, making this a multi-year project.

tanzania6bIt is speculated that these human prints may be the finest in the entire world of any age. Many prints had all the toes clearly visible. They appear to be the oldest modern human (Homo sapiens) prints but that will await confirmation of the samples of ash that we obtained. Preliminary sampling has placed the age of the footprints at approximately 80,000 years old, based on five 40Ar/39Ar incremental heating experiments on biotite separated from the footprint ash. Current fossil and genetic evidence point to the origin of modern humans in Africa about 200,000 years ago, suggesting the footprints most likely originate from Homo sapiens and, therefore, would be the oldest known footprints of our species. These footprints will be studied in detail to reconstruct gait, speed, and tentative body weight and height. Chemical composition of the ash will be compared to that of the regional volcanoes to determine the origin of the footprint-bearing ash. The findings will be submitted to one of the most prestigious scientific journals.

tanzania7After 6 days and delightful visits from the Maasai elders in the surrounding villages who promised to guard the prints, we left for Arusha. On the way, we stopped at Laetoli, the site of the oldest and most famous human prints, dating from 3.6 million years to very early ancestors of humans, the australopithecines. These print tracks are much shorter in length and now have been covered up since 1997 to protect them. However, the dirt used for cover had seeds in it and acacia trees sprung up causing root damage to the site. So a big controversy now is how to protect the prints we found and there is much speculation about how to do that. The president of Tanzania has declared that they cannot be covered so the public cannot see them. It is a biq question that is not answered yet.

tanzania8We also had a great side trip to Olduvai Gorge, the most famous site of early human fossils starting with the Leakeys in the 1930s and 40s. Louis Leakey’s son Richard, a very famous paleoanthropologist now about 65, has continued the work for almost 50 years. He was a speaker at the conference in Arusha that we attended after coming back where Dr. Liutkus presented the preliminary findings from our field work. He is a good friend of Dr. Rick Potts (Director of the Human Origins Program at The Smithsonian and close friend) and first suggested to Rick that Olorgesailie in the Kenyan Rift Valley area was a potentially good site over 20 yrs ago. It has been highly productive.

The trip home was LONG but uneventful, it was good to get home. I was ready for a good burger and pizza. It will be intriguing to see how this anthropological gold mine is further excavated and preserved.

Bibliography

1. Mietto, P., Avanzini, M. and Rolandi, G., 2003, Palaeontology: Human footprints in Pleistocene volcanic ash: Nature, v. 422, p. 133.

2. Leakey, M.D., and Hay, R.L., 1979, Pliocene footprints in the Laetolil Beds at Laetoli, northern Tanzania: Nature, v. 278, p. 317-323.

3. Behrensmeyer, A.K., and Laporte, L.F., 1981, Footprints of a Pleistocene hominid in northern Kenya: Nature, v. 289, p. 167-169.

4. Charteris, J., Wall, J.C., and Nottrodt, J.W., 1981, Functional reconstruction of gait from the Pliocene hominid footprints at Laetoli, northern Tanzania: Am J Phys Anthropol, v. 58, 133-144.

5. Leakey, M.D., 1987, The hominid footprints: in Laetoli, A Pliocene site in northern Tanzania (Leakey, M.D., and Harris, J.M., eds.), Oxford University Press, New York, NY, 584 pp.

6. Raichlen, D.A., Pontzer, H., and Sockol, M.D., 2008, The Laetoli footprints and early hominin locomotor kinematics: Journal of Human Evolution, v. 54, p. 112-117.

7. Laporte, L.F., and Behrensmeyer, A.K., 1980, Tracks and substrate reworking by terrestrial vertebrates in Quaternary sediments of Kenya: Journal of Sedimentary Petrology, v. 50, p. 1337-1346.

8. Deocampo, D.M., 2002, Sedimentary structures generated by Hippopotamus amphibius in a lake-margin wetland, Ngorongoro Crater, Tanzania: Palaios, v. 17, p. 212-217.

9. Ashley, G.M., and Liutkus, C.M., 2002, Tracks, trails, and trampling by large vertebrates in a rift valley paleo-wetland, lowermost Bed II, Olduvai Gorge, Tanzania: Ichnos, v. 9, p. 23-32.