Hominid Corridor Project
Hominid Corridor Project ( Engl. : Hominid Corridor Research Project , HCRP) is the name for an international long-term research project on fossil apes ( family Hominidae) and the human evolution in the African Great grave breach . The German-American- Malawian research cooperation in Southeast Africa has existed since 1983 and has been headed by Timothy Bromage ( New York University ) and Friedemann Schrenk ( University of Frankfurt am Main ). The best-known finds include the 2.5 million year old lower jaw UR 501 of a Homo rudolfensis and the 2.3 to 2.5 million years old upper jaw fragment RC 911 of a Paranthropus boisei in Malawi.
Selection of the research area
At the beginning of the 1980s there were three important regions in Africa for finding fossils of the hominini species: the longest known in the area of today's UNESCO World Heritage Site Cradle of Humankind in the north of South Africa near Makapansgat; 3000 km further north in Kenya ( Laetoli ) in the Olduvai Gorge ; and a site at the northeast end of the East African Rift in the Afar Depression in Ethiopia, which was only opened up since the early 1970s . From the fossil discoveries that had become known by then, Timothy Bromage and Friedemann Schrenk had derived the hypothesis that the elongated rift valley could have been a possible distribution corridor for the pre- and early-human species.
Using satellite images and older scientific descriptions of the geological conditions, they searched for layers of sediment that were around five to two million years old . An area on the northwestern shore of Lake Malawi in the area of the Malawi Rift proved to be particularly suitable :
- “The ditch very likely formed a water-bearing corridor between southern and eastern Africa, so our assumption, but in any case the narrowest possible migration route between the main discovery areas, which are far apart. Since we mainly wanted to reconstruct the changes in the habitat and the animal world as well as the routes of spread, there was no alternative to the Malawi Rift, no matter how poorly its fossils have been preserved. We named our research project the Hominid Corridor Project. "
The Malawi Rift was formed - like the entire African rift system - through the gradual sinking of the earth's crust as a result of the drifting apart of continental plates . Over hundreds of thousands of years, rock was removed from the lateral slopes and plateaus, washed towards the valley floor and deposited there as sediment. The sediments covered the remains of organisms and thus contributed to the fact that, among other things, pollen , bones and teeth were saved from complete destruction. Around 500,000 years ago, however, the northern section of the Malawi Rift was narrowed by tectonic processes, with the result that previously submerged layers of earth were raised again and are now on the earth's surface.
The sand-colored sediment mounds from the transition from the Pliocene to the Pleistocene have been referred to as Chiwondo Beds since the 1920s and represent three successive periods: the lowest and oldest layer is around four million years old; the top, youngest 1.6 million years; and in between there is a layer dated to an age of 3.8 to 2 million years.
However, the low density of fossils that emerge on the surface of the earth has proven to be a disadvantage: there is usually only one fragment per square kilometer, and fossils accumulate massively in only a few places.
Fossil Search
In cooperation with Malawian partners, including in particular the archaeologist Dr. Yusuf Juwayeyi from the State Authority for Antiquities, the selected, around 80 km long and 10 km wide area north of Lake Malawi was systematically explored from 1984 onwards. The National Geographic Society initially granted $ 9,000 for this as start -up funding. In groups of 20 to 30 trained, mostly local helpers, selected areas were paced square by square meter and all fossil remains that had been weathered out of the ground were collected. Only a few, particularly fossil-rich places were specifically dug. These "collections", some of which are repeated annually, make use of the process of soil erosion caused by rainfall , since new fossils are uncovered after each rainfall without human intervention and - since the area is unpopulated and unsuitable for arable farming due to its many calcareous sandstones - the area and remain in place for years.
Particularly numerous among the vertebrate fossils that have been recovered are mammals (around 75 percent), half of which belong to fossil antelopes . The other half of the mammal finds can be assigned to horses , pigs , giraffes , elephants , primates and hippos . Around a quarter of the fossils come from fish , turtles and crocodiles . The Chiwondo Beds also contain large amounts of fossil snail shells, which Lake Malawi washed up on its former shores in prehistoric times.
On the basis of the vertebrate fauna discovered in different soil layers, it was possible to reconstruct that there must have been a significant climate change in the region around 2.5 million years ago - parallel to an ice age in Europe : the proportion of animals is increasing significantly in the younger layers who lived in the open savannah; But even in this epoch there were areas with permanent access to the water as well as closed, dry bushland.
The composition of the fossil mammal fauna from the Chiwondo Beds could also be compared with fossil finds from southern and northeastern Africa, with the aim of clarifying the biogeographical relationships between these three regions:
- “The result: 14 species occurred in both eastern and southern Africa, three species were of purely South African origin and 17 of purely East African origin. The largest group formed a kind of rift “corridor” fauna, which is typical of the high and lowlands of East Africa. Thus we can this corridor as part of a succession of connected habitats ( habitats ) understand that stretched as a band from northeastern Africa to southeastern Africa. "
This finding was assessed as an indirect confirmation of the initial hypothesis that the elongated rift valley could also have been a distribution corridor of the pre- and early-human species. The hypothesis was immediately confirmed by the lower jaw UR 501 of a Homo rudolfensis found in 1991 in the very south of the study area near Uraha, a small village not far from Karonga , as well as the upper jaw fragment with two preserved molars - RC, which was recovered in August 1996 near the village of Malema by Stephen Mwanyongo 911 - of a Paranthropus boisei . In addition to the very old age of UR 501, which is 2.5 million years old, the special significance of both finds was that for the first time the coexistence of Homo and Paranthropus - two very different species of hominini - in south-east Africa was documented through neighboring localities of almost the same age could. This reinforced the theory that environmental influences - an expansion of the savannahs with the simultaneous loss of rainforests as a result of climate change - could have led to a specialization in the early species of the hominini: the development of food sources through an increasing specialization in the consumption of hard fiber plants in Paranthropus ; the development of food sources through the use of simple stone tools ( rubble tools ) in homo .
The discovery of UR 501 also had the consequence that the species Homo rudolfensis is now fossilized much earlier than Homo habilis , which until then had been considered the earliest species of the genus Homo .
literature
- Friedemann Schrenk , Timothy Bromage : The hominid corridor of Southeast Africa. In: Spektrum der Wissenschaft , No. 8/2000, pp. 46–53
- Friedemann Schrenk, Timothy Bromage: Adam's parents. Expeditions into the world of early humans. CH Beck, Munich 2002, ISBN 3-406-48615-0
Web links
- Official website
- Tooth for tooth. On further training in Africa ... (PDF; 3.0 MB) In: Impulse for Science 2011. From the work of the Volkswagen Foundation , pp. 42–47
- Senckenberg Research Institute: Friedemann Schrenk's website
Individual evidence
- ↑ Friedemann Schrenk , Timothy Bromage : The hominid corridor of Southeast Africa. In: Spectrum of Science , No. 8/2000, p. 47
- ↑ Oliver Sandrock, Ottmar Kullmer, Friedemann Schrenk, Yusuf McDadlly Juwayeyi and Timothy G. Bromage: Fauna, taphonomy, and ecology of the Plio-Pleistocene Chiwondo Beds, Northern Malawi. In: René Bobe, Zeresenay Alemseged and Anna K. Behrensmeyer (eds.): Hominin Environments in the East African Pliocene: An Assessment of the Faunal Evidence. Springer Verlag, Dordrecht 2007, pp. 315-332, ISBN 978-1-4020-3097-0 ; doi : 10.1007 / 978-1-4020-3098-7_12
- ↑ a b Schrenk & Bromage, The Hominid Corridor of South East Africa , p. 49
- ↑ a b Schrenk & Bromage, The Hominid Corridor of Southeast Africa , p. 48