Soa basin

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The Soa Basin is a basin west of the center of the elongated Indonesian island of Flores . It covers an area of ​​approximately 200 square kilometers and has long been known as a paleontological and archaeological site. The basin was named after the Soa community, which is at its western end.

For example , stone tools from the Old Pleistocene were found in 1994 and 1997 on the upper reaches of the Ae Sissa River, in the area of ​​the Mata Menge site , which , according to zircon fissure traces dating , are 880,000 ± 70,000 to 800,000 ± 70,000 years old BP . Stone tools from the Wolo Sege site in the vicinity of Mata Maß are even older ; they were dated to 1.02 ± 0.02 million years ago in 2010. These finds are evidence of a very early colonization of the island by groups of hominini and thus of a potentially possible gradual " island dwarfing " of their descendants on Flores, whose presumably last descendants - Homo floresiensis - about 100 kilometers west of the basin in the Liang Bua cave were discovered.

In 2016 it became known that 700,000 year old hominine fossils were recovered from the Mata Quantity site, which may have belonged to the ancestors of Homo floresiensis .

Location and geology

Soa Basin (Lesser Sunda Islands)
Soa basin
Location of Wolo Sege
Location of Wolo Sege
The Soa Basin on Flores Island

The Soa basin, around 20 × 10 kilometers in size, is formed today by the river called Ae Sissa and its tributaries, which drain to the northeast to the Floresee . Above its southwestern end is the city of Bajawa , south of the Ngada village Boawae. The basin is at a height of up to 400 meters above sea level, the adjoining mountain ranges reach up to around 1000 meters, some volcanoes - some still active, some inactive - are more than 2000 meters high. In the basin, numerous small hills tower over the otherwise flat, savannah- like grassland , in which, however, deep gorges have repeatedly been cut by the waters.

The geological stratification of the Soa Basin consists of two large stratigraphic units. On the one hand, there is the basement , known as the Ola Kile Formation , consisting of andesitic breccias , deposits of pyroclastic flows and lahars with occasionally embedded siltstone , sandstone and rock from former lava flows , the minimum age of which is 1.86 ± 0.12 million years. Above this basement lies the much younger Ola-Bula Formation , an approximately 100-meter-thick layer of varying proportions, partly of volcanic origin, partly from deposits from rivers or lakes. You sit on a cap made of limestone (called Gero Limestone), which has also formed in a body of water.

The sediments of the Soa basin suggest that for most of its existence it contained a large lake or a chain of smaller lakes that dried out at irregular intervals as a new drain cut into the surrounding mountains. After that, as in the present, a grassy landscape developed that was eroded away while sediment had previously been deposited in the waters.

History of exploration

The first fundamental field studies in the Soa basin were carried out in the mid-1950s by the Catholic priest Theodor Verhoeven , who studied ancient history at the University of Leiden and carried out research for his master's thesis in Pompeii . Verhoeven had been made aware by the Raja of Nagakeo that there, near the abandoned village of Ola Bula, the bones were exposed due to erosion. The result of his large-scale excavations - especially finds of Stegodon - bone - published Verhoeven first time in 1958. It was followed in 1960 geological surveys by the Geological Survey of Indonesia , the results of 1961, among other things, the appointment of the two soil formations (Ola-Kile- and OLA Bula formation).

In 1963, Verhoeven uncovered stone tools, including choppers and hand axes, for the first time, 3.5 kilometers west of his first excavation site at the sites known as Mata Menge and Boa Lesa, along with other Stegodon fossils . Verhoeven concluded that Stegodon and early individuals of the genus Homo had coexisted on Flores. Because it had been proven on Java that Homo erectus and Stegodon coexisted there around 750,000 years ago, Verhoeven also suspected that the stone tools of Flores were similarly old and that Homo erectus had therefore also colonized Flores. However, two in 1970 jointly published with the priest Johannes Maringer Fundberichte remained unnoticed in circles of paleoanthropologists because of dating distrusts and it was assumed that the stone tools in deeper, coincidentally Stegodon- could be advised leading soil layers. In addition, Flores was completely surrounded by water even during the Ice Ages , and Homo erectus was not believed to be able to build ocean-going watercraft.

The Soa basin did not move into the focus of research again until the early 1990s, when Paul Sondaar (1934–2003) from the University of Utrecht , a student of Gustav Heinrich Ralph von Koenigswald with a special interest in the process of island dwarfing , visited Mata Menge in their neighborhood a new site - Tangi Talo (also: Bhisu Sau) - opened up, where he discovered fossils of a dwarf stegodon and a giant tortoise. In 1985, while excavating in the Grotta Corbeddu in Sardinia , Sondaar accidentally came into contact with Verhoeven, who - long since retired - was visiting the excavations. Thereby Sondaar learned of the assumption that Homo erectus could have reached Flores 750,000 years ago, which in turn suggested to him that the dwarf stegodons on Flores could have become extinct as a result of the colonization by Homo erectus ; younger Stegodon fossils were significantly larger than the older ones, which was attributed to an immigration of large individuals after the dwarf forms became extinct. In 1992 and 1994, field studies by Sondaar, Fachroel Aziz and others actually showed that stone tools and Stegodon bones recovered from Mata Menge are around 730,000 years old; but this dating was also initially doubted by experts. Only after an age determination of further finds by zirconium fissure trace dating was published in the scientific journal Nature , the colonization of Flores by individuals of the genus Homo was recognized already during the Old Pleistocene .

An excavation campaign supported by the Australian Research Council followed from 1998 to 2001 under the direction of Fachroel Aziz and Mike Morwood , in the course of which the Soa basin was re-mapped and documented by aerial photographs. During this time, among other things, 16 Stegodon sites were developed and all fossil sites were radiometrically dated. Further excavations took place between 2003 and 2006, which now primarily served the purpose of clarifying the settlement history - immigration and extinction - of Homo erectus . This project, also financed by the Australian Research Council, also included excavations on Java and other areas of Flores, including the Liang Bua cave , in which Theodor Verhoeven had already unearthed fossils in 1965 - and the first remains of in 2003 Homo floresiensis were found.

Funding for a third excavation campaign in the Soa Basin has been running since 2010 and until 2015 with funds from the Australian Research Council under the leadership of Mike Morwood, Adam Brumm and Gert van den Bergh, which aims, among other things, to find fossil evidence for the existence of early representatives of the genus Homo . For this purpose, a total of 2000 square meters of vegetation and younger layers of earth were cleared using bulldozers , after which more than a hundred local helpers systematically dug the ground. After hundreds of stone tools and thousands of animal fossils, the fossil remains of at least three individuals of the genus Homo - one adult and two children - were actually recovered in October 2014 .

literature

  • Lost World of the Little People. National Geographic, April 2005
  • Robert G. Bednarik: The maritime dispersal of Pleistocene humans. In: Migration and Diffusion. Volume 3, No. 10, 2002, pp. 6-33.

Web links

Individual evidence

  1. ↑ a b Mike J. Morwood et al .: Fission-track ages of stone tools and fossils on the east Indonesian island of Flores. In: Nature , Volume 392, 1998, pp. 173–176, doi: 10.1038 / 32401
    Images of the stone tool finds from Mata Menge discovered in 1994 (from: Mike J. Morwood et al., 1998)
  2. ^ A b Adam Brumm, Gitte M. Jensen, Gert D. van den Bergh, Michael J. Morwood, Iwan Kurniawan, Fachroel Aziz, Michael Storey: Hominins on Flores, Indonesia, by one million years ago. In: Nature , Volume 464, 2010, pp. 748–752, doi : 10.1038 / nature08844
    Hobbit ancestors: A million years ago people lived on the Indonesian island of Floresheise. On: heise.de from March 20, 2010
  3. ↑ a b Gerrit D. van den Bergh et al .: Homo floresiensis-like fossils from the early Middle Pleistocene of Flores. In: Nature. Volume 534, 2016, pp. 245–248, doi: 10.1038 / nature17999
  4. ↑ a b Fachroel Aziz and Michael J. Morwood: Introduction: Pleistocene Geology, Palaeontology and Archeology of the Soa Basin, Central Flores, Indonesia. In: Fachroel Aziz, Michael J. Morwood and Gert D. van den Bergh (Eds.): Pleistocene Geology, Palaeontology and Archeology of the Soa Basin, Central Flores, Indonesia. Publication of the Center for Geological Survey, Ministry of Energy and Mineral Resources, Republic of Indonesia, Special Publication No. 36, 2009, pp. 1-17. ISSN  0852-873X
  5. ^ Theodor Verhoeven: Pleistocene finds in Flores. In: Anthropos , Volume 53, 1958, pp. 264-265
  6. ↑ Johannes Maringer, Theodor Verhoeven: The stone artifacts from the Stegodon fossil layer from Mengeruda on Flores, Indonesia . In: Anthropos , Volume 65, 1970, pp. 229–247
    Johannes Maringer, Theodor Verhoeven: Note on some stone artifacts in the National Archeological Institute of Indonesia at Djakarta, collected from the Stegodon-fossil bed at Boaleza in Flores. In: Anthropos , Volume 65, 1970, pp. 638-639
  7. ^ Paul Yves Sondaar et al .: Changement de faune au Pléistocène moyen et colonization de l'île de Flores (Indonésie) par Homo erectus. In: Comptes rendus de l'Académie des sciences. Series 2. Sciences de la terre et des planètes , Volume 319, No. 10, 1994, pp. 1255-1262, ISSN  1251-8050
  8. ^ University of Wollongong , Dump of February 13, 2012: In search of the first Asian hominins: excavations in the Soa Basin of Flores, Indonesia.
  9. ↑ Ewen Callaway: Hobbit relative hint at family tree. In: Nature. Volume 534, No. 7606, 2016, pp. 164-165, doi: 10.1038 / 534164a