Thursday, April 8, 2010

Tugen Hills; origin of the early man

Courtesy: Safari ya Baringo & www.diplomatie.gouv.fr/en/article
Following several excavations of ancient hominids and other material in Tugen Hills, researchers now are convinced that this area is the cradle of modern mankind.
Located in the north rift region of Kenya, the Tugen Hills consist of a series of tilted blocks in the Gregory Rift Valley. Deposits have accumulated in the resulting tectonic depressions dating to between 16 mya and the present day. In 2000, in the Lukeino Formation, which dates back to 6 mya, the remains of a bipedal hominid, Orrorin tugenensis, were found. This has had the effect of completing altering concepts about our distant origins. Our efforts have thus focused on this geological formation, and we have been rewarded with the discovery of a form closely resembling the gorilla on the Kapsomin site.

Palaeontology





Fig. 35: tusk of hippopotamid

A rich and very diversified fauna was recovered in the Lukeino Formation (Fig. 35), including numerous bovids (impalas, duikers, tragelaphini), tragulidae, tree hyraxes, cercopithecidae (colobinae), galagos, rodents, leporids and a number of carnivores including tree civets, suids, rhinocerotids, hippopotamids, birds and crocodiles. At Cheboit, the site that supplied the first hominid tooth of the formation in 1974, we found a further chalicothere alongside traditional Lukeino fauna.




Geology

The almost continuous sequence at the Tugen Hills spans the period between 16.5 mya and the present day and is the most complete series currently identified in Africa for the period in question (Fig. 31).






Fig. 31: dating of Lukeino Formation

Human palaeontology

Hominids
Following the first discovery in 1974 by M Pickford of a hominid lower molar in the Lukeino Formation at Cheboit, work understandably began on this formation, where the remains of the first bipedal hominid dating to 6 mya were uncovered in three other locations (Kapsomin, Aragai, Kapcheberek) in autumn 2000.
The Orrorin mandible has quite a high body (primitive feature) with no diastema. The fairly small and quadrangular molars are covered with thick enamel, and the enamel-dentine junction is fairly flat. The premolars have offset roots, as in the great apes, and the modestly sized canines are also similar to those of the great apes. The characteristics of the premolars and canines are not, however, similar to those of chimpanzees but rather are inherited features from their Miocene ancestors who already displayed these traits. As for the lower incisors, they appear to be closer to hominid incisors.
The skeletal remains suggest that the hominid displayed adaptations to bipedalism and arboreal locomotion. Bipedalism is suggested by the morphology of the femur neck, its extension, the cortical bone distribution (thicker at the base of the neck and less so at the top), muscular insertion of the gluteal and obturator externus muscles, and the orientation of the femoral head (Fig. 37).





Fig. 37: Thighbones of a chimpanzee (left) and Orrorin tugenensis (right)
Great apes
In the Middle Miocene levels of the Ngorora Formation (12.5 mya), a molar that is morphologically similar to that of the chimpanzee was uncovered. The resemblance to the European Dryopithecus (about 9 to 11 mya) suggests that the latter are probably not ancestors of the African hominoids, but their descendants. On the Kapsomin site, an upper incisor and a lower-molar fragment, which are similar to those of the modern gorilla, were discovered recently (Fig. 39).






Fig. 39




Palaeoenvironment

The Lukeino Formation was formed in a wet environment as indicated by faunal remains which include water chevrotains, palm civets, fruit bats, tree hyraxes, and numerous types of colobus and impala. These faunae suggest a fairly wooded and wet environment. The existence of a forest is confirmed by well-preserved plant remains in diatomaceous layers. In particular, a number of leaves in the process of precise determination have been found, some of which are of significant size, at around 10cm or so, with clearly defined dripping points. They are also extremely diversified with almost 15 or so identifiable types. Lastly, a hot and wet environment is suggested by significant deposits of rubified palaeosols in the upper levels of the Lukeino Formation. The first bipedal hominids were therefore not associated with dry environments.
In addition, a number of petrified-algae limestone blocks found in the formation indicate that there were hot springs in the environment, as confirmed by the thin film of bacterial sediment covering certain specimens of mammal (hominids included). The environment in the Tugen Hills 6 million years ago must have been fairly similar to the current environment in the Lake Bogoria region of Kenya with lower cliffs and more dense forest coverage around the edges of the lake (Fig. 42).






Fig. 42



Taphonomy

At Kapsomin, a number of fossils showed traces of predation, which suggests that a large feline was responsible for the build-up of bones. The only modern feline that kills its prey and carries it back to a chosen spot is the leopard. It carries mid-sized prey, such as antelopes, up trees, where it keeps them for later meals. Scraps occasionally fall to the ground where hyenas and jackals either eat them immediately or make away with them. However, if pieces fall into water, then they have a better chance of being preserved, and that is why we find fossilised bones particularly at Kapsomin. One possible scenario to explain this is that a tree was growing on a low basalt cliff at the foot of which there was a shallow body of water. A leopard or similar beast hid its prey in a tree, and pieces fell on occasion into the water where they were perfectly preserved. During other periods, the water level receded and pieces fell onto dry ground where they were damaged by carrion feeders, by desiccation (the hominid mandible is cracked similar to Bovid mandibles) and by being trampled or even carried away.

Museology

In the context of collaboration with Community Museums of Kenya, a new museum was established in association with the French Natural History Museum, the French Ministry of Foreign Affairs and a number of local sponsors (Banque Crédit Agricole IndoSuez, Bamburi Cement, the Commercial Bank of Kenya, the French Embassy in Nairobi, Michelin). Located in Kipsaraman, 6km from the fossiliferous sites, it is intended for the protection of existing and fossil heritage. It is divided into two major parts: one part is devoted to the protection of existing biodiversity (presented via a series of panels; this part was provided by the French Natural History Museum in Paris), and the other part presents the geological and palaeontological history of the region with reference to local legends. The museum receives schools, students from the university in Eldoret and tourists alike. It is a source of information and education for local people.





Following several excavations of ancient hominids and other material in Tugen Hills, researchers now are convinced that this area is the cradle of modern mankind.
Located in the north rift region of Kenya, the Tugen Hills consist of a series of tilted blocks in the Gregory Rift Valley. Deposits have accumulated in the resulting tectonic depressions dating to between 16 mya and the present day. In 2000, in the Lukeino Formation, which dates back to 6 mya, the remains of a bipedal hominid, Orrorin tugenensis, were found. This has had the effect of completing altering concepts about our distant origins. Our efforts have thus focused on this geological formation, and we have been rewarded with the discovery of a form closely resembling the gorilla on the Kapsomin site.

Palaeontology





Fig. 35: tusk of hippopotamid

A rich and very diversified fauna was recovered in the Lukeino Formation (Fig. 35), including numerous bovids (impalas, duikers, tragelaphini), tragulidae, tree hyraxes, cercopithecidae (colobinae), galagos, rodents, leporids and a number of carnivores including tree civets, suids, rhinocerotids, hippopotamids, birds and crocodiles. At Cheboit, the site that supplied the first hominid tooth of the formation in 1974, we found a further chalicothere alongside traditional Lukeino fauna.




Geology

The almost continuous sequence at the Tugen Hills spans the period between 16.5 mya and the present day and is the most complete series currently identified in Africa for the period in question (Fig. 31).






Fig. 31: dating of Lukeino Formation

Human palaeontology

Hominids
Following the first discovery in 1974 by M Pickford of a hominid lower molar in the Lukeino Formation at Cheboit, work understandably began on this formation, where the remains of the first bipedal hominid dating to 6 mya were uncovered in three other locations (Kapsomin, Aragai, Kapcheberek) in autumn 2000.
The Orrorin mandible has quite a high body (primitive feature) with no diastema. The fairly small and quadrangular molars are covered with thick enamel, and the enamel-dentine junction is fairly flat. The premolars have offset roots, as in the great apes, and the modestly sized canines are also similar to those of the great apes. The characteristics of the premolars and canines are not, however, similar to those of chimpanzees but rather are inherited features from their Miocene ancestors who already displayed these traits. As for the lower incisors, they appear to be closer to hominid incisors.
The skeletal remains suggest that the hominid displayed adaptations to bipedalism and arboreal locomotion. Bipedalism is suggested by the morphology of the femur neck, its extension, the cortical bone distribution (thicker at the base of the neck and less so at the top), muscular insertion of the gluteal and obturator externus muscles, and the orientation of the femoral head (Fig. 37).





Fig. 37: Thighbones of a chimpanzee (left) and Orrorin tugenensis (right)
Great apes
In the Middle Miocene levels of the Ngorora Formation (12.5 mya), a molar that is morphologically similar to that of the chimpanzee was uncovered. The resemblance to the European Dryopithecus (about 9 to 11 mya) suggests that the latter are probably not ancestors of the African hominoids, but their descendants. On the Kapsomin site, an upper incisor and a lower-molar fragment, which are similar to those of the modern gorilla, were discovered recently (Fig. 39).






Fig. 39




Palaeoenvironment

The Lukeino Formation was formed in a wet environment as indicated by faunal remains which include water chevrotains, palm civets, fruit bats, tree hyraxes, and numerous types of colobus and impala. These faunae suggest a fairly wooded and wet environment. The existence of a forest is confirmed by well-preserved plant remains in diatomaceous layers. In particular, a number of leaves in the process of precise determination have been found, some of which are of significant size, at around 10cm or so, with clearly defined dripping points. They are also extremely diversified with almost 15 or so identifiable types. Lastly, a hot and wet environment is suggested by significant deposits of rubified palaeosols in the upper levels of the Lukeino Formation. The first bipedal hominids were therefore not associated with dry environments.
In addition, a number of petrified-algae limestone blocks found in the formation indicate that there were hot springs in the environment, as confirmed by the thin film of bacterial sediment covering certain specimens of mammal (hominids included). The environment in the Tugen Hills 6 million years ago must have been fairly similar to the current environment in the Lake Bogoria region of Kenya with lower cliffs and more dense forest coverage around the edges of the lake (Fig. 42).






Fig. 42



Taphonomy

At Kapsomin, a number of fossils showed traces of predation, which suggests that a large feline was responsible for the build-up of bones. The only modern feline that kills its prey and carries it back to a chosen spot is the leopard. It carries mid-sized prey, such as antelopes, up trees, where it keeps them for later meals. Scraps occasionally fall to the ground where hyenas and jackals either eat them immediately or make away with them. However, if pieces fall into water, then they have a better chance of being preserved, and that is why we find fossilised bones particularly at Kapsomin. One possible scenario to explain this is that a tree was growing on a low basalt cliff at the foot of which there was a shallow body of water. A leopard or similar beast hid its prey in a tree, and pieces fell on occasion into the water where they were perfectly preserved. During other periods, the water level receded and pieces fell onto dry ground where they were damaged by carrion feeders, by desiccation (the hominid mandible is cracked similar to Bovid mandibles) and by being trampled or even carried away.

Museology

In the context of collaboration with Community Museums of Kenya, a new museum was established in association with the French Natural History Museum, the French Ministry of Foreign Affairs and a number of local sponsors (Banque Crédit Agricole IndoSuez, Bamburi Cement, the Commercial Bank of Kenya, the French Embassy in Nairobi, Michelin). Located in Kipsaraman, 6km from the fossiliferous sites, it is intended for the protection of existing and fossil heritage. It is divided into two major parts: one part is devoted to the protection of existing biodiversity (presented via a series of panels; this part was provided by the French Natural History Museum in Paris), and the other part presents the geological and palaeontological history of the region with reference to local legends. The museum receives schools, students from the university in Eldoret and tourists alike. It is a source of information and education for local people.



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