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john hawks weblog

paleoanthropology, genetics and evolution

Photo Credit: Landscape of the Omo Kibish Formation, Ethiopia. John Hawks [CC-BY-NC-ND]

My travels in Ethiopia

I spent the last week trekking through southern Ethiopia.

My trip started with some bad luck. A flat tire on Interstate 90 outside Chicago made me miss my plane. The polar vortex delayed getting the car serviced, pushing my schedule back a whole day. I had planned a short trip for filming followed by some time in the National Museum in Addis Ababa. The day’s delay required some rearrangement of plans, and my filming friends made an extraordinary offer: Why not come south to the Omo Valley for the week?

John Hawks overlooking Omo Kibish formation
A photo taken by my new Nyangatom friend

The Omo has been important to paleoanthropology since the late 1960s. In 1967, the International Omo Research Expedition brought together field teams from America, France and Kenya to find fossil hominins in this part of the country. They had considerable success. The Shungura Formation produced a good sample of hominins from the Late Pliocene and earliest Pleistocene, between around 2.6 million and 1.8 million years ago. These included the teeth and jaws of a robust australopithecine, probably A. boisei, and some less robust teeth that arguably may represent an early form of Homo. Work continued on the Shungura Formation until the mid-1970s, and field teams have returned to the region in recent years.

The Omo Valley also has much later fossil deposits. The Kibish Formation stretches between around 100,000 and 200,000 years ago, from the late Middle to early Late Pleistocene. Richard Leakey’s group within the International Omo Research Expedition discovered two hominin fossil specimens in the Kibish Formation: a partial skeleton and skull of a modern human, and a partial skull of a second human. These became known as Omo 1 and Omo 2. Leakey’s investigation was limited to the 1967 field season. Afterward, he went to Lake Turkana, establishing what became his much more famous field area at Koobi Fora.

Omo 2 site at Omo Kibish
Omo Kibish Formation near the Omo 2 site

John Fleagle returned to the Omo Kibish area with a team in 1999 to work out the age of the Kibish Formation. The team would eventually determine that the two specimens are nearly 200,000 years old, making them among the earliest – at the moment, the earliest – modern human fossil specimens known. However, the two skulls are “modern” in only certain anatomical features. They represent an early modern human population that is substantially diverse, in which the anatomical pattern common throughout the world today was only beginning to emerge.

The Omo Valley still takes time to reach today. Our caravan of three 4x4s took three days to drive from Addis Ababa out to the Omo Kibish field site. Along the way one of our vehicles was sidelined by a broken differential. Our guide replaced it quickly with one of the local minibuses, which proved to be much hardier on the rough roads than we expected!

Lovely hill for a breakdown
Lovely hill for a breakdown

Regular gravel roads connect the major towns on the eastern side of the river, though most villages are accessible only by tracks. Road construction was going on everywhere, it seemed, from the main road down to Arba Minch, further south to Konso, and even between Turmi and Omorate, the town furthest south along the Omo in Ethiopia. Roadbeds are being rebuilt with heavy equipment and prepared for paving. A few sections along the main route are already paved, but where construction is underway traffic is diverted onto temporary tracks parallel to the main road. These are slow-going.

A ferry at Omorate is presently the main way within Ethiopia to reach the western side of the lower Omo valley. A bridge has been in the works for many years but stands stalled in mid-construction north of the town. The ferry took a while, but served admirably for us to reach the less accessible western side of the river.

Ferry across the Omo River at Omorate
Ferry across the Omo River at Omorate

The last 70 km up to the field area was very rough and rarely traveled. While we were in the area, the archaeologists’ vehicles were the only ones we saw. Large areas west of the river have been intensively grazed by goats, so that during the dry season the dust is very thick. We drove on tracks with dust several inches thick, and kicked up huge foggy clouds of it as we went.

John Hawks in Omorate with the dust of travel
Me in Omorate, covered with the dust from the road

We encountered warm, friendly people everywhere throughout southern Ethiopia. The Omo Kibish area is presently inhabited by the Nyangatom people, who live principally by herding goats, donkeys and cattle. The Omo River itself is the main source of water in the area during the dry season. Nyangatom boys brought their herds of goats down to the water every day.

Omo River, tree with exposed roots (left)
Omo River

When we reached the Omo Kibish area, we met up with John Fleagle and John Shea at their archaeological field camp. They are surveying some of the known sites from the Omo Kibish Formation, reassessing the potential for archaeological excavation. The area is rich with Middle Stone Age-era artifacts, and survey seems very promising.

Omo Kibish overlook at sunrise
A view over the Omo Kibish camp area at sunrise

John and John were kind enough to give us an overview tour of the two original excavation sites where Omo 1 and Omo 2 were found. These are on opposite sides of the Omo River, giving us a chance to do a river crossing in the camp motorlaunch. It was great to see these field localities and get a feel for the contexts of the human fossil remains.

John Fleagle and John Shea in the field at Omo 1
John Fleagle (left) and John Shea (right) at the Omo 1 excavation site

Single, well-defined fossil-bearing layers have extensive exposures around the sides of the hillocks, bluffs and valley walls. The fossils represent an alternation of shoreline and swampy environments. I saw crocodile, hippopotamus, fish and bird fossils, with some beautifully preserved. At the time when these sediments were deposited, the Omo Kibish area was the northernmost extent of Lake Turkana, where the ancient Omo was dropping thick sediments as it entered the still waters of the lake. The climate fluctuated widely across the time period from 200,000 to 100,000 years ago. The Omo Kibish area underwent successive periods of deposition, when the lake was large, followed by erosion as the ancient Omo and its tributaries cut down through new sediments. New flood layers swept right across the eroded topography, and in some cases you can see them draped across ancient hills and valleys.

Omo Kibish stratigraphy showing unconformity
Omo Kibish stratigraphy showing unconformity, layers above are draped over the earlier landscape.

Peppered through the stratigraphy are ancient volcanic ashfalls. These provide a context for dating the deposits.

Ancient people were using this area throughout, leaving stone artifacts. It is amazing walking along the exposures, noting the stones that are the marks of ancient human activity. These early modern humans were making fundamentally the same kinds of artifacts that we find across western Eurasia, made by the earliest Neandertals, and across most of the African continent at the same time. There were regional differences in the pattern of toolmaking, but there was a broad technological commonality. This was the cultural background of our ancestors.

Omo River sunrise, sunbeams
Omo River sunrise