Nariokotome boy

from Wikipedia, the free encyclopedia
KNM-WT 15000: the Nariokotome boy

Nariokotome boy or Turkana boy refers to the fossil of a male, juvenile individual of the genus Homo , whose exceptionally completely preserved skeleton was discovered in August 1984 in Kenya on the dry river Nariokotome , around 5 km west of Lake Turkana . Because of its anatomical features, the skeleton is either attributed to Homo erectus , or it is assigned to Homo ergaster by those researchers who name particularly old African finds of this species .

Until the announcement of the findings of Homo naledi in 2015 - apart from around 100,000 year old Neanderthal skeletons - no comparable fully preserved skeleton of a chronospecies of the genus Homo had been discovered.

discovery

On August 22, 1984, Kamoya Kimeu discovered a small, rectangular, two and a half by five centimeter fragment of a hominine frontal bone on a tree-lined hill ; the search for further surface finds was unsuccessful. Kimeu was the head of a group of Kenyans, who had long worked for Louis Leakey and later for Richard Leakey , whose task it was to search the earth's surface for fossils, to mark hominine finds and thus to make them accessible to scientists. Kimeu was also so experienced that he correctly identified the find as belonging to Homo erectus due to its inner wall, which had become smooth from the pressure of the brain (the corresponding bones of pigs or gazelles are rough on the inside) and the thickness of the bone . Richard Leakey, holder of the excavation license for the area on the Nariokotome river bed explored for the first time and experienced in the retrieval of fossils, and the paleoanthropologist Alan Walker , responsible for the first morphological evaluation of bone finds, were both in Nairobi on that day to do work to be done in the laboratory and in the office. Informed by radio of the find, both flew to the Nariokotome camp the next day.

On August 24th, Kimeu's helpers began to clear the site of the browbone from stones, branches and other material, to remove the top layer of soil and to shake all the excavated material away from the site through sieves. In fact, while sifting, further fragments of the frontal bone were discovered, as well as the right temporal bone (the part of the skull that surrounds the right ear) and the right and left parietal bones (the roof of the skull). All fossils undoubtedly belonged to Homo erectus , a first estimate of their age based on the soil layers by the geologist Frank Brown showed 1.2 million years. Leakey then informed the National Geographic Society , one of the funders for the excavations, who sent their photographer David Brill to the Nariokotome camp, in the hope of being able to document the recovery of further finds for the readers of National Geographic magazine . After Brill had reached the camp, the excavations continued, and in fact the second temporal bone was found, pieces of a cheekbone and several other bone fragments, finally also the largely completely preserved upper jaw without protruding wisdom teeth - an indication that it was the fossil acted by a youth. When the upper jaw was discovered, initially only the left half was accessible; the right half was in the roots of an acacia tree , i.e. in an undisturbed layer of soil that made it possible to reliably date the fossil.

As the first pieces from the area below the head, several ribs were discovered a little later : Ribs are considered to be particularly unusual finds, because Homo erectus did not bury his dead, they were - like all other animals - gnawed by scavengers in order to reach the internal organs reach; in addition, rib bones are usually not hard enough to fossilize. But it was only when a piece of a shoulder blade was recovered that it became apparent that it could be a sensational find - the first skeleton of a Homo erectus and - after Lucy - only the second fossil skeleton of an individual from human ancestry. Shortly thereafter, other parts of the skeleton were exposed: a vertebral bone and the right ischial bone (part of the pelvis ). Until September 1st, a. further vertebral bones and several complete ribs were discovered, also parts of a sacrum and the lower end of a tibia . This was followed by the thigh bones, the second shin, two intact collarbones , the humerus and the lower jaw. A large, round footprint over the humerus was from a hippopotamus that had stepped on the body; it had pushed arm and shoulder blade into the mud, helping preserve those bones. At the same time, the excavators found a part in freshwater living apple snail of the genus Pila : A proof that the corpse of the young people located in the water and his bones were conserved among mud. The excavations were temporarily terminated on September 21, 1984 - in fact, the find, which its discoverers referred to as the “Nariokotome boy”, was the best-preserved skeleton of an early hominini individual at this point in time. In the following four years until 1988, however, more bones were recovered by removing and sifting the entire find mound - 1,400 cubic meters of earth and stones - by hand. In the end, only a few vertebrae and ribs were missing, as well as the small hand and foot bones, which were probably the first to be eroded out of the earth and trampled by the hooves of the Turkana goats, which had frequented the hill.

features

The assembled fragments of the skull
Forensic reconstruction of the skull

67 of a total of 206 bones and 12 teeth were discovered. If the around 100 missing hand and foot bones are disregarded and if one considers that the second half of the body can also be reconstructed using the bones of one half of the body, then the skeleton below the skull is almost two thirds complete. The skull was broken into around 70 fragments; the pronounced bulge above the eye and especially the narrow pelvic girdle prove that the fossil of a boy was found.

The scientific name of the find is KNM-WT 15000, the place of storage is the Nairobi National Museum (formerly: Kenya National Museum , hence KNM; WT for the west side of Lake Turkana).

In the first description , the fossil was placed on Homo erectus and dated 1.6 million years ago. The age of the adolescent at the onset of death was initially estimated at 11 to 13 years and his height at 169 cm due to the permanent molars and his bone structure that had not yet fully erupted (the epiphyseal plates of the long arm and leg bones had not yet been replaced by bone tissue). In a later analysis, the age at death was calculated to be 8 to 9 years based on the growth lines of the tooth enamel , the height was given as 141 to 147 cm and an age of 1.53 ± 0.05 million years for the fossil was given. The initial misjudgment of age was based on the fact that the progress of the ossification of his skull sutures known from Homo sapiens was initially transferred to the Nariokotome boy. A precise analysis of the growth lines of the tooth enamel, however, revealed indications that its physical development was much faster than in anatomically modern humans, that childhood was much shorter then than it is today.

As an adult, according to an estimate published in 2015, the Nariokotome boy would have become 176 to 180 cm tall and weigh 80 to 83 kg; a further study from 2018 confirmed this estimate, but increased the range to 160 to 177.7 cm for the body height and 60 to 82.7 kg for the weight. An obvious cause of death could not be proven. However, signs of gum disease were discovered in the right lower jaw. The x-ray showed that the boy had lost a milk molar a month before his death, but two parts of the root remained in the jaw. This resulted in an infection and an abscess, which could be fatal even 300 years ago.

There was at least one rib from each (but the lowest) pair of ribs. The thorax could therefore be precisely reconstructed and proved in all aspects to be indistinguishable from that of a modern person. However, the Nariokotome boy - like many species of apes - still had six lumbar vertebrae instead of mostly five in Homo sapiens . The wedge-shaped vertebral bodies (in the chest area towards the front of the body a little flatter than behind, in the lumbar area towards the front slightly thicker than behind) mean that the spine (unlike the non-human great apes) was curved in an S-shape similar to that of Homo sapiens ( Kyphosis and lordosis ).

The physique of the Nariokotome boy (slim and tall), which can be reconstructed on the basis of the bones, was compared with the physique of people who now live in different climate zones. According to this, his physique can be interpreted as an adaptation to tropical temperatures: “The boy was probably running around in a hot, open landscape and sweating . The overall build indicates that the boy (and Homo erectus in general) has already lost his fur or body hair. […] Since there was no body hair to protect him from the burning equatorial sun, the boy probably had a very dark skin color. Another fascinating feature that indicates adaptation to a hot and dry environment is the nose. The boy had a real nose. ”Older species like Australopithecus and Homo habilis , on the other hand, did not have a protruding nose, but a flat, monkey-like nose that is less suitable for moistening dry air before it reaches the lungs. This interpretation is also in line with the fossil plant finds.

The skull is very similar to the Homo erectus finds from Asia, especially to the Java people . Bernard Wood suggested in 1992 that the fossil - together with other finds of comparable age and appearance - should be assigned to Homo ergaster , a species whose characteristics, however, were never clearly delineated from Homo erectus and other similarly old species of hominini .

The reconstruction of the skull suggests an internal volume of approx. 880 cm³, which in adults would probably have increased to approx. 910 cm³ (for comparison: the brain volume of modern humans is approx. 1400 cm³). The structure of the pelvis , the shoulder joints and the large arm and leg joints are consistent with a - in contrast to the species of the genus Australopithecus - very extensive adaptation to a two-legged mode of locomotion. A particularly noticeable difference to modern humans is that the vertebral canal is much narrower than that of Homo sapiens . CT scans of the semicircular canals of the vestibular system also exhibited characteristics of which as a result of evolutionary adaptation can be interpreted to permanently-upright posture: how anatomically modern humans has also Nariokotome boy compared with gorillas and chimpanzees front a larger and posterior semicircular canal and a smaller lateral semicircular canal. In her book Turkana Boy. In their search for the first human , Alan Walker and Pat Shipman warn against comparing too far: “The Turkana boy was an animal the size of a human being, he looked like a human being, but he didn't have our brains, and with It is almost certain that he did not behave like a human. "

See also

literature

  • Richard Leakey and Alan Walker: Unearthed: A Fossil Skeleton 1,600,000 Years Old. In: National Geographic. November 1985 (with photos by David L. Brill).
  • Alan Walker , Richard E. Leakey (Eds.): The Nariokotome Homo erectus Skeleton. Springer, Berlin and Heidelberg 1993, ISBN 978-3-662-10384-5 (also: Harvard University Press, Cambridge, MA, USA, 1993).
  • Alan Walker, Pat Shipman: Turkana Boy. In search of the first person. Galila Verlag, Etsdorf am Kamp 2011, ISBN 978-3-902533-77-7 (revised German edition of The Wisdom of Bones , Weidenfeld & Nicolson, London 1996).
  • M. Christopher Dean and B. Holly Smith: Growth and Development of the Nariokotome Youth, KNM-WT 15000. In: Frederick E. Grine, John G. Fleagle , Richard E. Leakey (Eds.): The First Humans. Origin and Early Evolution of the Genus Homo. Springer, Dordrecht 2009, pp. 101–120, ISBN 978-1-4020-9979-3 , doi: 10.1007 / 978-1-4020-9980-9_10 .
  • Ronda R. Graves et al .: Just how strapping was KNM-WT 15000? In: Journal of Human Evolution. Volume 59, No. 5, 2010, pp. 542-554, doi: /10.1016/j.jhevol.2010.06.007 .

Web links

Individual evidence

  1. ↑ pronounced as a six-syllable word: na-ri-o-kot-o-me
  2. ^ A b Frank Brown , John Harris, Richard Leakey and Alan Walker : Early Homo erectus skeleton from west Lake Turkana, Kenya. In: Nature . Volume 316, 1985, pp. 788-792, doi: 10.1038 / 316788a0
  3. ↑ The description of the discovery follows Alan Walker, Pat Shipman: Turkana Boy , pp. 21-40.
  4. ^ Alan Walker, Pat Shipman: Turkana Boy , 39.
  5. ↑ James C. Ohman et al .: Stature-at-death of KNM-WT 15000. In: Human Evolution. Volume 17, No. 3-4, 2002, pp. 129-141, doi: 10.1007 / BF02436366 .
  6. ^ Ian Tattersall : The Strange Case of the Rickety Cossack - and Other Cautionary Tales from Human Evolution. Palgrave Macmillan, New York 2015, ISBN 978-1-137-27889-0 , p. 152.
  7. ↑ Christopher B. Ruff and M. Loring Burgess: How much more would KNM-WT 15000 have grown? In: Journal of Human Evolution. Volume 80, 2015, pp. 74-82, abstract
  8. ↑ Deborah L. Cunningham et al .: The effect of ontogeny on estimates of KNM-WT 15000's adult body size. In: Journal of Human Evolution. Volume 121, 2018, pp. 119–127, doi: 10.1016 / j.jhevol.2018.04.002
  9. ^ Alan Walker, Pat Shipman: Turkana Boy, p. 41.
  10. ^ Alan Walker, Pat Shipman: Turkana Boy, pp. 285, 290-291.
  11. ^ Alan Walker, Pat Shipman: Turkana Boy , p. 235.
  12. ↑ Java Man and Turkana Boy. A comparison of the Homo erectus finds from Africa and Asia on talkorigins.org
  13. ^ Bernard Wood : Origin and evolution of the genus Homo. In: Nature. Volume 355, 1992, pp. 783–790, full text (PDF) ( Memento from September 13, 2014 in the Internet Archive )
  14. ^ Damiano Marchi et al .: Relative fibular strength and locomotor behavior in KNM-WT 15000 and OH 35. In: Journal of Human Evolution. Volume 131, 2019, pp. 48-60, doi: 10.1016 / j.jhevol.2019.02.005
  15. ^ Alan Walker, Pat Shipman: Turkana Boy, p. 296.
  16. ^ Alan Walker, Pat Shipman: Turkana Boy, p. 252.