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Hominin fossil siteKenya

Koobi Fora

Koobi Fora is a fossil-rich stretch of the east shore of Lake Turkana in northern Kenya. Since 1968 it has yielded hundreds of hominin fossils, mostly from about 2 to 1.4 million years ago, when early Homo and Paranthropus boisei lived side by side, along with some of the oldest stone tools and butchered bones.

Site label

3.95° N, 36.19° E
Where
Kenya
Type
Hominin fossil site
Coordinates
3.95° N, 36.19° E
Map point
Marker is a point inside a large research area on the east shore of Lake Turkana.
Wikidata
Q1968136

Koobi Fora in brief

Koobi Fora is the name of a ridge and a sandspit on the eastern shore of Lake Turkana, in the far north of Kenya, and of the wider fossil area around them. The rocks here, called the Koobi Fora Formation, are close to 600 metres of lake and river sediment laid down between about 4 and 1 million years ago. Layers of volcanic ash run through them, and those ash layers can be dated, which means a fossil found in the right layer can be given an age.

No other place in Africa has told us more about the period from about 2 to 1.4 million years ago, when several kinds of early human lived around the same lake at the same time.

How the work began

In 1968 the paleoanthropologist Richard Leakey borrowed a small helicopter from an American team working across the border in Ethiopia and landed near Ileret, at the north end of the area. He found fossils and stone tools almost at once. That year he set up a base camp on the Koobi Fora spit, and in 1969 the Koobi Fora Research Project began, led by Leakey for the fossils and Glynn Isaac for the archaeology. The project continues today. In 1973 the Kenyan government protected the area as Sibiloi National Park.

The lake itself was called Lake Rudolf until the 1970s, which is why many older papers refer to “East Rudolf”.

The fossil finders

Most of the hominin fossils from Koobi Fora were found by a small team of Kenyan field workers led by Kamoya Kimeu, known in the field as the “Hominid Gang”. They walked the eroding slopes looking for bone on the surface, and they became so skilled that Leakey arranged anatomy classes so they could recognise fragments they had not seen before.

The most famous example is KNM-ER 1470. In 1972 Bernard Ngeneo noticed pieces of skull on a slope that others had passed over. The skull was rebuilt from hundreds of fragments and turned out to have a larger brain than anyone expected for its age.

Key finds

Fossils from the area are catalogued with the prefix KNM-ER, for Kenya National Museums, East Rudolf.

  • KNM-ER 406. A skull of Paranthropus boisei, found in 1969, with the broad face and huge cheek teeth typical of the species.
  • KNM-ER 1470. A skull about 1.9 million years old, found in 1972. Leakey first placed it in Homo habilis; many researchers now put it in a separate species, Homo rudolfensis. Its exact age caused years of argument (see below).
  • KNM-ER 1813. A smaller-brained skull of about the same age, usually classed as Homo habilis. Together, 1470 and 1813 are one reason scientists think more than one kind of early Homo lived at the same time.
  • KNM-ER 3733. A skull about 1.7 million years old, found by Ngeneo in 1975 and classed as early Homo erectus. It showed that erectus and Paranthropus boisei shared this landscape.
  • KNM-ER 741. Part of a shin bone about 1.45 million years old. In 2023 Briana Pobiner and colleagues showed that nine marks on it were made by stone tools. They are the first cut marks found on an early hominin limb bone, and among the oldest signs of one hominin butchering another.
  • Older fossils. At Allia Bay, in the south of the area, fossils of Australopithecus anamensis date to about 4.2 to 3.9 million years ago.

The famous skeleton known as Turkana Boy (KNM-WT 15000) was found in 1984 by Kamoya Kimeu on the west side of the lake, at Nariokotome, so it is not a Koobi Fora fossil, though it is often mentioned with it.

The KBS Tuff argument

The first volcanic ash layer studied here is called the KBS Tuff, after the geologist Kay Behrensmeyer, who also found the first stone tools at Koobi Fora. In the early 1970s it was dated to about 2.6 million years ago. Because skull 1470 lay below it, that would have made 1470 extraordinarily old, older than any other Homo known at the time.

Other researchers disagreed, and the argument ran through the 1970s. Better dating, along with comparisons of pig fossils from different sites, finally settled the KBS Tuff at about 1.87 to 1.89 million years. The long dispute helped push forward the dating methods (potassium-argon and argon-argon) that the whole field now relies on.

Stone tools and cut marks

Koobi Fora is just as important for archaeology as for fossils. Stone tools from just above the KBS Tuff are among the older tools known from East Africa. In the 1970s and 1980s, studies of animal bones from Koobi Fora and Olduvai Gorge found cut marks made by stone tools, some of the first clear evidence that early humans were butchering animals for meat. A site complex called FxJj 20 has burned material from about 1.5 million years ago that some researchers read as early control of fire, though this is still debated.

Scientists learn to read cut marks by making them. Researchers butcher modern carcasses with copies of ancient stone tools, record the marks, and compare them with the fossils.

Two species, one shoreline

In 2024 a team led by Kevin Hatala reported footprints at Koobi Fora about 1.5 million years old, pressed into mud at the edge of the ancient lake. One trail of 12 prints has a different walking pattern from three single prints made within hours of it. The team suggests the trail was made by Paranthropus boisei and the single prints by Homo erectus. If that is right, it is the first time two hominin species have been caught on the same surface at almost the same moment. Footprints cannot prove which species made them, so this is a strong hypothesis rather than a settled fact.

What it was like to work there

I spent six weeks at Koobi Fora in 1999 on a university field school, and went back a few years later with Louise Leakey (I tell more of that story on the About page).

On the way north we spent about a week in the bush, then drove for three days across the middle of Kenya. One day out there the truck broke down, and the repair was going to take a long time. One of our guides climbed down with his rifle, barefoot, and walked back to camp on his own, in the heat, in the middle of the bush with predators around. I have never forgotten it.

The base camp sits right on the shore of Lake Turkana. We slept in tents, washed and swam in the lake every day, and some people fished and spearfished. The toilets were stone stalls, and the washing water was piped up from the lake (not for drinking). There was no phone signal, and this was before most people had cell phones anyway. We were really far away. For a night or two we camped up near Ileret, carrying all our own water.

The heat is different from home. There is usually a steady wind, so your sweat dries before you notice it. You never feel drenched, and that is the danger: you have to keep drinking all day.

What amazed me most was the fossils. There are millions of bone fragments just lying on the ground. Most are loose on the surface, washed out of the slopes, so there is no way to tell which layer they came from or how old they are. The Kenyan members of the team could look at a tiny scrap and tell you, more or less, what animal it came from. That is how new sites are found.

Today the east shore is dry, rocky and almost bare. Two million years ago it was green, with rivers, woodland and grassland around the lake. Sitting and looking out at the water, trying to picture that, is one of my favourite memories.

Visiting

Koobi Fora lies inside Sibiloi National Park, which is part of the Lake Turkana National Parks World Heritage Site, listed by UNESCO in 1997. In 2018 the site was added to UNESCO’s list of World Heritage in Danger, mainly because the Gibe III dam upriver in Ethiopia has changed the flow of water into the lake.

The National Museums of Kenya runs a small museum and research base on the Koobi Fora spit, and Kenya Wildlife Service park fees apply. Getting there is the hard part: the drive from Nairobi takes days on rough roads, and the alternative is a flight of two to three hours by light aircraft. Check current access and safety with Kenya Wildlife Service before planning a trip.

Sources

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