Significations et usages de Turkana_Boy

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Turkana Boy

Catalog number	KNM-WT 15000
Common name	Turkana Boy
Species	Homo erectus or Homo ergaster
Age	1.6 mya
Place discovered	Lake Turkana, Kenya
Date discovered	1984
Discovered by	Kamoya Kimeu/Richard Leakey

Turkana Boy, also occasionally, Nariokotome Boy is the common name of fossil KNM-WT 15000,^[1] a nearly complete skeleton of a hominid who died in the early Pleistocene. This specimen is the most complete early human skeleton ever found. It is 1.5 million years old.^[2] Turkana Boy is classified as either Homo erectus or Homo ergaster.

His age has been estimated from 7 years six months to as old as 15 years. The most recent scientific review suggests 8 years of age.^[3] It was initially suggested that he would have grown into 1.85 m tall adult but the most recent analysis argues for the much shorter stature of 1.63 m.^[3] The reason for this shift has been research showing that his growth maturation differed from that of modern humans in that he would have had a shorter and smaller adolescent growth spurt.^[3]

The skeleton was discovered in 1984 by Kamoya Kimeu, a member of a team led by Richard Leakey, at Nariokotome near Lake Turkana in Kenya.^[4]

  Adolescence and maturity

The shape of the pelvis identifies that the specimen was a male. His estimated age at death depends upon whether the maturity stage of his teeth or skeletal is used, and whether that maturity is compared to that of modern humans or chimpanzees.^[3] A key factor here is that while modern humans have a marked adolescent growth spurt, chimpanzees do not. While initial research assumed a modern human type of growth, more recent evidence from other fossils suggests this was less present in early Homo. This affects the estimation of both his age and his likely stature as a fully grown adult.^[3]

• Anthropologists Alan Walker and Richard Leakey in 1993 estimated the boy to have been about 11–12 years old based on known rates of bone maturity.^{[5][nb 1]}
• Christopher Dean (M. C. Dean) of University College London, in a Nova special, stated that Turkana Boy was 8 years old at death.^[6][7] Alan Walker and Richard Leakey, though, explain that dental dating often gives younger than actual ages.^{[8][nb 2]}
• Ronda Graves and colleagues in the most recent review of the problems involved conclude that he would "have grown an additional five to 14 cm before reaching adulthood" and that "if, at death, he was eight to ten years of age, [he would have been] 154 cm tall, and growing faster than a modern human but slower than a chimpanzee. According to this scenario, KNM-WT 15000 would have attained an adult stature ranging between 159 cm and 168 cm." Moreover that "according to our preferred models of growth and development, [his] growth in stature [would have been] completed by 12 years of age (4 years after death), so that the majority of growth has already occurred.^[3]

  Morphology

The specimen comprises 108 bones, making it the most complete early human skeleton discovered. The skeleton is about 1.60 m (5 ft 3 in) tall. In adulthood, Turkana Boy might have reached 1.85 m (6 ft 1 in) tall and massed 68 kg (150 lb).

The pelvis is narrower than in Homo sapiens, which might indicate more efficient running^{[citation needed]}, whether to run down small game or to avoid predators. Turkana Boy's people might have hunted more than did Homo habilis. The Boy was relatively tall, which would have increased his surface area and helped him to dump heat.^[9]

Body hair may also have been thinner to hasten cooling. In The Evolution of Bipedality and Loss of Body hair in Hominids, P. E. Wheeler suggests that body hair was lost in the shift towards savanna living. In equatorial Africa, modern humans evolved this trait an estimated one million years ago.^{[citation needed]} However, more recent research indicates that Ardipithecus ramidus developed bipedality for moving through trees about 4.4 million years ago.^[10]

The overall KNM-WT 15000 skeleton still had features (such as a low sloping forehead, strong brow ridges, and the absence of a chin) not seen in H. sapiens. The arms were slightly longer. Turkana Boy had a projecting nose rather than the open flat nose seen in apes.^{[9][not in citation given]}

  Vocal capabilities

The fossil skeleton and other fossil evidence such as Acheulean stone tools prompt the majority of scientists to conclude that Homo ergaster and Homo erectus - unlike their more primitive ancestors – became efficient hunters. The social structure would probably have become more complex with a larger brain volume; the Broca's area of the brain allows speech and is noted by a slight slant on the cranium. However, there are different views on the origin of language:

• 1.9 million years ago (Homo habilis had a large Broca's area able to be seen in the cranium of KNM ER 1813), possible signs of the earliest ability for speech.
• 1.5 million years ago, on the arrival of several distinct more human-like hominins spread throughout Africa, Europe, and Asia (i.e., Homo erectus).
• 600,000 and 150,000 years ago when archaic Homo sapiens dominated regions in the Pleistocene epoch (several members during this period are considered fully modern Homo sapiens)^{[citation needed]}
• 50,000 years ago (fully modern Homo sapiens had already spread through the Old World and slowly into the New World 20,000 BCE. Some believe language coincided solely with modern humans once culture was established by groups such as Cro-Magnon man in Europe. It is still a matter of debate whether Neanderthals had a modern form of language.

Turkana Boy's thoracic vertebrae are narrower than in Homo sapiens.^[11] This would have allowed him less motor control over the thoracic muscles that are used in modern humans to modify respiration to enable the sequencing upon single out breaths of complex vocalizations.^[12]

  See also

• List of fossil sites (with link directory)
• List of hominina (hominid) fossils (with images)

  Notes

1. ^ Walker explains: "in KNM-WT 15000, his skeletal development can only be used to place an upper limit of about 14 years on his age at death. However, a less often recognized skeletal maturational event does generally occur prior to 14 years in modern males-- the union of the trochlea and capitulum (and also the lateral epicondyle) of the humerus, prior to their joint union with the humeral shaft.... That these elements were fused in KNM-WT 15000 (at least the capitulum and trochlea) suggests a skeletal age for him of somewhat more than 11 years.... In either event, 11 to 12 years would seem to be the best compromise figure to use for his chronological age at death."(Walker & Leakey, 1993, p. 235)
2. ^ "Just as in the case of human dental age (above), estimates based on tooth formation give slightly younger ages than those based on emergence." (Walker & Leakey, 1993, p. 207)

  Footnotes

  References

• Leakey, Richard (1994). The Origin of Humankind. ISBN 0-465-03135-8. 
• Leakey, Richard. Origins Reconsidered. ISBN 0-385-41264-9. http://books.google.com/books?id=rGo8AAAACAAJ&dq=origins+reconsidered&ei=gY_QSJmpPIPWtgOD8eTbAw. 
• Barraclough, G. (1989). Stone, N. (ed.). ed. Atlas of World History (3rd edition ed.). Times Books Limited. ISBN 0-7230-0304-1. 
• Walker, Alan; Shipman, Pat. Wisdom of the Bones. ISBN 0-679-74783-4.  - Good popular level presentation
• Alan Walker and Richard Leakey (eds.), ed. Nariokotome Homo erectus Skeleton. ISBN 0-674-60075-4.  - Technical papers
• Mckie, Robin (2000). Dawn of Man. BBC. ISBN 0-7894-6262-1. 
• Wheeler, P.E. (1984). The Evolution of Bipedality and Loss of Functional Body Hair in Hominids t 13, 91-98. Journal of Human Evolution. ISBN 0047-2482-84-01009-1. 
• Lewin, Roger (2004). Human Evolution: An Illustrated Introduction 5th Edition. Wiley. ISBN 978-1-4051-0378-7. 

  External links

• http://www.amnh.org/exhibitions/permanent/humanorigins/history/turkana.php
• Turkana Boy
• http://www.rps.psu.edu/sep98/missing.html
• http://www.findarticles.com/p/articles/mi_m1511/is_n3_v18/ai_19160830
• http://www.archaeologyinfo.com/homoerectus.htm