Our Lake Turkana ANCESTORS

 

"Today Lake Turkana lies in the midst of a dry, hostile desert environment. But this was not always the case.

About two million years ago, the lake was much larger and the surrounding area was greener, Since then, rapid changes to the climate have periodically caused the lake to shrink, and occasionally it has disappeared altogether.

During the wetter times, it was an ideal place for early humans to live, and when they died it was a perfect place for their remains to fossilise. That is because Lake Turkana lies in a volcanic area, where tectonic activity can move earth's crust and create new layers. It is within these layers that fossils from different time periods are found."

TURKANA BASIN ― CLIMATIC TIMELINE

(mya = million years ago,  kya = thousand years ago)

c. 4.5 mya   One of the earliest paleoenvironments of the Turkana basin was the Apak floodplain of the Pliocene epoch. Around 4.5 million years ago the ancestral Omo, Turkwell, and Keiro rivers were joined to form the Turkana River. Turkana basin has yielded fossils of whale and stingray, marine animals that suggest Turkana River drained into the Indian Ocean.

[Australopithicus anamensis 4.2 mya]

c. 4.1 mya  Later in  the Pliocene a large body of water, Lonyumun Lake, covered the Turkana basin for about 100,000 years, drowning many terrestial habitats of forest and grassland. Remainders of these habitats exist on the margins of the basin but the chief fossils are fish and molluscs.

c. 3.5 mya  Even later in the Pliocene, Lokochot Lake, appeared and disappeared within 60,000 years. Fossils preserved in the sediments relate to extinct hominin.

[Kenyanthropus platyops 3.5 mya]

c. 2.4 mya  Mount Kulal, an active volcano, dominated Turkana basin during the late Pliocene and early Pleistocene. Fossils unearthed on the Tulu Bor flood plain are embedded in tuff, hardened volcanic ash.

c. 1.9 mya  Lorenyang Lake, a large body of water in the Turkana basin, formed during the Pleistocene and existed for about 400,000 years. Fossils from this period are varied and numerous, from extinct hominin to organisms they may have eaten, fish and shellfish, plants and birds.

[Homo habilis ('handyman'), or H. rudolfensis, 1.9 mya]

[Archeulean hand-axes, 1.76 mya]

c. 1.5 mya  Lorenyang Lake eventually filled with sediment and was succeeded by the Char floodplain. Fossilised footprints indicate that at least some hominins were walking upright at this time.

[Homo erectus 1.5 mya]

c. 9.0 tya  'Mega-Lake' Turkana emerged during the African Humid Period. The climate produced a rich array of resources, aquatic and wetland plant and animal species, a reliable source of freshwater, and grasslands for 'hunters and fishers. Existing populations of crocodiles and Sudanian fish species are evidence of previous connection with Sobat and Nile River system.

c. 7.5 tya  Mega-Lake Turkan dried up almost completely, splitting into two shallow lakes.

The fluctuating climatic conditions for Lake Turkana have been a feature for at least 4.5 million years and continue into the present. Today the area covered by water is about half the mega-lake boundaries of the earliest Holocene and African Humid Period. For all its changes, however, it has remained a geological trap, and now tells the story of humanity ― the evolution of 'Us', from the first bipedal hominins to the appearance of Homo sapiens at 200,000 years ago (and the beginnings of our dispersal about 100,000 years ago).

Despite this breathtaking scale of evidence, it is important to understand that the fossil record from the Turkana basin is not a continuous record. As the meteorological and geological evidence is variable (and the conditions for life in this place altered dramatically), so too the evolution from hominids to humans is indirect and dynamic. Human ancestry is not a linear process. Populations of ape-like creatures inhabited and left. They prospered and died out. All we really know is that different branches of our development existed here at particular times. But Lake Turkana remains a special place, because it was here that so much of the story was able to be worked out.

LAKE TURKMANA ― DISCOVERY TIMELINE

1968   Excavations at the lake started in 1968 when Richard Leakey led a group tom the western side known as the Koobi Fora. Aerial views had suggested that there were lots of fossils to be found. The first few years were "a bit of an adventure", but before long fossils of numerous species "were tumbling out of the ground".

1972   Travelling backward  to 1.9 million years ago ... some small but tantalizing fossils ... "We had fragments of the front of the skull, fragments of the back of the skull, fragments of the side of the skull". Over the weeks they unearthed more fragments. At the end of each day, Richard Leakey flew them out to camp, where Meave Leakey cleaned them and pieced them together. From 150 fragments, Meave reassembled a hominid  whose brain was larger than others. Richard named it as a species called Homo habilis, or 'handy man', capable of making and using stone tools. 'Skull 1470' as it was called, has since been classified as Homo rudolfensis, from the colonial name for Lake Turnaka.

1984   Travelling a little forward from there in geological time to 1.5 million years ago we meet a young male who looked surprisingly like we do. Meave Leakey remembers, "The initial discovery of Turkana Boy was a small fragment of skull that my colleague Kamoya ... A few weeks ... everything we were finding from individual vertebrates to individual limb bones ... in association with a skull and a jaw. So complete. It was a young boy. At death, probably standing about five foot three inches ... He would've grown into an individual maybe five foot six ... It wasn't us. Perhaps a brain size of a two year old child today. It wasn't fully us in terms of the body, but very like us." This almost complete skeleton was Homo erectus.

1995   "And then this jaw turned up". Meave Leakey and her team had found fossils of Australopithicus anamensis, a truly ancient individual. "There were two volcanic ashes ... most of the fossils came from between the two ... And it dates just less than 4.2 million years." Before anamensis, our ancestors used their arms for support walking on all fours, not two legs. "A tibia we found ... very, very modern looking. From the shape of the top end and the bottom end, anamensis is definitely a bi-ped ..." This was the very earliest hominid yet discovered that scientists widely agree walked up front, half a million years before the nearest contender.

1999   Also on the western side of the lake, Meave and her team discovered another ancient relative, called Kenyanthropus platyops, or 'flat-faced man', dated 3.5 million years old.

2011   Discovery of earliest known Acheulean hand-axes, multi-functional tools, dated 1.76 million years ago.

2015   Discovery of oldest known stone tools dated 3.3 million years ago. Which is earlier than any Homo-species. This is significant because it was formerly thought technology only appeared with Homo hablis, Homo erectus, etc.

[REFERENCES:

'Paleogeography of Lake Turkana', 19 Oct 2023, National Geographic

'Discoveries at Lake Turkana', 20 May 2022, National Geographic

'The Importance of Lake Turkana', 9 December 2015, BBC Online (Bradshaw Foundation)].

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BREAKING  BAD

WESTERN TURKANA, KENYA

"In Africa, the site of NATARUK provides the closest parallel of interpersonal violence to Jebel Sahaba. Situated west of Lake Turkana and dating to around 10.5 - 9.5 ka, the individuals found in Nataruk appear to exhibit signs of violent death through projectile impact marks (punctures and perforations), sharp and blunt force trauma, and fractures."

M Mirazo Lahr et al (22!), 2016, 'Inter-group violence among early Holocene hunter-gatherers of West Turkana, Kenya', Nature, 529.304 <doi 10.1038/nature16477>

[article text is edited i.e. condensed quotation].

Researchers remain deeply divided as to whether antagonistic relations formed a significant element of social life in prehistory. Human remains from the site of Nataruk record the intentional killing of a small band of foragers, providing unique evidence of a warfare event among hunter-gatherers. In 2012 the remains of 27 individuals were discovered partly or completely exposed on the surface of a gravel ridge. An age estimate of c. 9,500 - 10,500 years BP (or 7,500 - 8,500 BCE) for the victims of Nataruk is consistent with dates on shells, barbed-bone harpoons, and charcoal from sites in the immediate vicinity. It also corresponds to a phase of early Holocene high levels of Lake Turkana.

The group comprised 21 adults and six children (5 under 6 years). The children were found comingled or in close proximity to the remains of four adult women and two fragmentary adults of unknown sex. The remains of a 6 to 9 month old fetus were recovered from within  the abdominal cavity of one of the adult females, representing a 28th individual. No standardised orientation or position of head, face, or body was observed. With no evidence of deliberate burial, the bodies were preserved where they fell.

Ten of the 12 skeletons that were partly preserved articulated in situ show evidence of major traumatic lesion that would have been lethal in the immediate to short term. These included five, possibly six, cases of sharp-force trauma to the head and/or neck probably associated with arrow wounds, five cases of blunt-force trauma to the head, two cases of possible ante-mortem depressed bilateral fractures of the knees, two cases of multiple fractures to the right hand, and a case of fractured ribs. Only two of these skeletons in situ show no apparent evidence of peri-mortem trauma, although in both cases the position of the hands suggest the individuals may have been bound at the time of death. A total of four individuals, two males and two females, share this feature. In all of the cases of cranial trauma, the compression of bones is localised and cannot be explained by taphonomic forces, as unaffected cranial elements retain their original size and shape around the fractured portions.

Three artefacts were found within or embedded in two of the bodies: an obsidian bladelet embedded in one of the male crania, and two microliths; a chert lunate and an obsidian trapeze found inside the pelvic and thoracic cavities of a male skeleton. All three showed impact scars. Obsidian is relatively rare in other early Holocene later Sone Age sites of southwest Turkana, suggesting that the two groups confronted at Nataruk had different home ranges. The presence of projectile points embedded within the skeletal remains or within the body cavity is considered diagnostic of inter-group conflict, while fractures resulting from blunt and sharp force trauma, particularly to the head, neck, ribs, and hands, are indicative of deliberate violent trauma (ie inflicted with intent rather than spontaneous outburst of anger or accident).

"Nataruk may offer evidence ... of a standard antagonistic response to an encounter between two social groups ... important for the particular circumstances that preserved an ephemeral, but perhaps not unusual, event in the life of prehistoric foraging societies ... testimony of the antiquity of inter-group violence and war."

BAD TO THE BONE

NILE VALLEY, SUDAN

"The graveyard of Jebel Sahaba, Sudan, where 23 of 58 bodies [prior to 2022 reassessment; now 41 of 61 bodies] show evidence of violence, stands as the best example of extremely rare evidence for group-violence among prehistoric hunter-gatherers. The Jebel Sahaba remains were estimated to have a late Pleistocene age (often quoted as 14,000 - 12,000+ years) on the basis of the lithics industry. The Jebel Sahaba individuals were buried, separately or in small groups, presumably by their own community, after the raids or feuds in which they died."

Isabelle Crevecoeur et al (5), 2022, 'New insights on interpersonal violence in the Late Pleistocene based on the Nile Valley cemetery of Jebel Sahaba', Nature, 11.9991, <doi 10.1038/nature16477>

[article text is edited and reduced i.e. 'condensed quotation']

For the first time since Wendorf's 1965-1966 Nile Valley excavations (Wendorf F, 1968, The Prehistory of Nubia, vol 2, pp 954-1040), and his 2012 donation of all archives, artefacts, and skeletal remains to the British Museum, a complete reassessment has been conducted to clarify the nature, extent and dating of the violence experienced by the individuals buried at the site.

Previously (1968), abundant lithic artefacts were discovered within the physical space of the bodies, where the soft tissue would have once been, or directly embedded in the bones. Given their position, these stone specimens could not be considered to be grave goods. Re-examination of the evidence (2022) has determined a further 106 lesions, including 52 that can now be interpreted as Projectile Impact Marks. That is, another 21 individuals had clear signs of interpersonal violence/trauma in addition to the 20 described earlier. Three-quarters of the adults (n = 43) and half of the underage individuals had signs of peri-mortem trauma (unhealed injuries and projectile impact marks) or a combination of healed and unhealed traumas (ante and peri traumas).

At Jebel Sahaba, the co-occurrence of healed and unhealed traumas strongly supports sporadic and recurrent episodes of interpersonal violence between Nile Valley groups at the end of the late Pleistocene (direct radiocarbon dates from 18,740 ± 600 years BP to 10,032 ± 468 years BP). The projectile nature of at least half of the lesions suggest inter-group attacks, rather than intra-group or domestic conflicts (once again, use of arrows is normally diagnostic of planned or pre-meditated violence). This is confirmed by the identification of different lithics industries, associated with distinct semi-sedentary hunting-fishing-gathering groups. 

The frequency of healed wounds also shows that these attacks were not always lethal and could occur several times during the life of an individual. Similarly, although there were instances of double or multiple burial implying simultaneous deaths, grave-disturbance caused by subsequent internments does not support a single catastrophic event or massacre. Severe territorial competition between the local communities seems likely to have caused repeated disputes resulting in violent conflict.

Just as has been argued for the later Nataruk - Turkana experience, it appears the Jebel Sahaba cemetery-individuals reflect events not entirely unexpected in the life of prehistoric societies. Interpersonal, intergroup violence was probably an ephemeral, possibly even endemic, feature of prehistoric existence. 

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ANCIENT HOMININ CO-EXISTENCE

"There must have been genetic continuity between modern humans and the common ancestor we share with chimpanzees ... However the clear evidence for taxic diversity in the human clade [aka hominins] means that we also have close relatives who are not our ancestors ...

INTRODUCING Paranthropus boisei, a distinctive and long-extinct non-ancestral relative that lived alongside our early Homo ancestors (Homo hablis and Homo erectus) in eastern Africa."

Teeth, skull and jawbone fossils of P. boisei have been found from Ethiopia in the north, in Kenya and Tanzania, through to Malawi in the south, along a massive fault line called the East Africa Rift Valley. The species was originally classified as Zinjanthropus bosei , then Australopithecus boisei, and now Paranthropus boisei. Most of what we know about them comes from fossils excavated from Koobi Fora on the eastern shore of Lake Turkana and sites in the Nachukui Formation on the western side of the lake. 

Significant physical features include:

     a small brain ― not much bigger than that of a gorilla and about a third of the size of a modern human, 

      flat and broad face, large attachment areas for chewing muscles, small incisors with exceptionally large premolar and molar teeth crowns ― a large, thick, lower jaw combine with massive, molar, grinding teeth ―

     flexed cranial base ― the foramen magnum, where the brain connects with the spinal cord on the underside of the skull ― is situated almost as far forward as it is in modern humans, indicating that P. boisei was capable of walking on its hind legs.

"Several lines of evidence suggest that P. boisei acquired its distinctive morphology within an ecosystem that was trending towards cooler, drier, more open conditions [from rainforest to tropical grassland], which in turn led to an increase in C₄ vegetation ... Most C₄ biomass in the tropics are grasses or sedges and the chewing-dominated dentition would have enabled it to process this (which given the strength of the C₄ signal may have been their staple diet)."

In summary, P. boisei was a herbivore, processing a bulky but relatively low quality diet by mastication (i.e. without the advantage of rumenism, or digesting roughage in a series of stomachs, that other plains-grazers developed). However, they were bipedal which would have extended their range for foraging. 

"Preserved in dried out layer of sand and silt, the team found a trackway consisting of 12 footprints, evidently left by one individual walking in a straight line. There were also three isolated footprints near the main group ... The isolated tracks resemble those left by modern humans: the heel struck the ground first, then the foot rolled forwards before pushing off with the sole. Hatala and his colleagues suggest that these were made by Homo erectus ... In contrast, the continuous trackway was made by a more flat-footed hominin. Hatala and his colleagues suggest this could have been Paranthropus boisei ... It seems like these two species were co-existing with one another for more than 100,000 years ... "

(New Scientist, 2024)

     "On the TS2 surface ['stratigraphically about 10 m below the Elomalig'a Tuff, recently dated to ~1.52 million rears ago'], we uncovered one continuous trackway made by a single hominin individual and three isolated hominin tracks that, based on size and orientations, appeared to represent three additional, different individuals. The TS2 surface also includes 61 bird, 30 bovid, and 3 equid tracks ...

     Animals were walking and standing in shallow water or very close to the shoreline on a wet substrate that was supportive but deformable. After the tracks were formed, the surface was gently covered with fine sand and silty sand and preserved under the accumulating strata ...

     The lack of mud cracking and rooting indicates that the TS2 surface was subaqueous or minimally subaerially exposed, and limited overprinting suggests a short time interval between track formation and burial (hours to a few days) ...

     Longitudinal arching of human tracks is the product of heel-sole-toe rollover kinematics ... When looking broadly at the entire known sample of 1.4 to 1.6 Ma East Turkana hominin footprints, we now recognise two different patterns of bipedal kinematics ... variable heel strike patterns ... differences in push-off kinematics ...Based on [different foot morphology and function] we hypothesize that the HT1 trackway was created by P. boisei and the isolated TS2 tracks by H. erectus ...

     Presumably the lake margin and deltaic environments where the co-occurring tracks are recorded ... offered resources that were accessible and desirable to both taxa despite apparent adaptive differences ... We hypothesize low to neutral competition between these genera ... given their apparent adaptations for consuming different dietary resources."

(Science, 2024)

RESOURCES

BA Wood & DB Patterson, 2020, 'Paranthropus through the looking glass', PNAS, 117.38.

R Bobe et al (4), 2020, 'Early Hominins and Paleoecology of the Koobi Fora Formation, Lake Turkana, Kenya', African Paleoecology and human evolution.

M Marshall, 2024, 'Ancient footprints show how early human species lived side by side', New Scientist.

KG Hatala et al (18), 2024, 'Footprint evidence for locomotor diversity and shared habitats among early Pleistocene hominins', Science, 386, 1004-1010.