Turkana Boy

Turkana Boy, Nariokotome Boy

File:Turkana Boy.jpg
Catalog number	KNM-WT 15000
Common name	Turkana Boy, Nariokotome Boy
Species	Tentatively assigned Homo ergaster
Age	1.6 mya
Place discovered	Lake Turkana, Kenya
Date discovered	1984
Discovered by	Kamoya Kimeu/Richard Leakey
Image is of a cast on display at the American Museum of Natural History

Turkana Boy, now called, Nariokotome Boy, is the common name of fossil KNM-WT 15000, a nearly complete skeleton of a hominin youth who lived during the early Pleistocene. This specimen is the most complete early human skeleton ever found. It is believed to be between 1.5 and 1.6 million years old.

Estimates of his age at death range from seven to 18 years old; the most recent scientific review suggests eight years. It was initially suggested that he would have grown into a 185 centimetres (73 in) tall adult, but the most recent analysis argues for the much shorter stature of 163 centimetres (64 in). 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 briefer and smaller adolescent growth spurt.

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.

Adolescence and maturity

The shape of the pelvis identifies the specimen as male. Estimates of the age at death depend on whether the maturity stage of the teeth or skeleton is used, and whether that maturity is compared to that of modern humans or to chimpanzees. A key factor 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.

• 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.
• Christopher Dean (M. C. Dean) of University College London, in a Nova special, stated that Turkana Boy was 8 years old at death. But Alan Walker and Richard Leakey said that dental dating often gives a younger age than a person's actual age.
• Ronda Graves and colleagues in the most recent review of the problems involved concluded 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 centimetres (61 in) 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 centimetres (63 in) and 168 centimetres (66 in)." 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".

Morphology

Nariokotome Boy reconstruction

Forensic facial reconstruction

Steps of facial reconstruction

The specimen comprises 108 bones, making it the most complete early human skeleton discovered. The skeleton is about 160 centimetres (63 in) tall. In adulthood, Turkana Boy might have reached 185 centimetres (73 in) tall and massed 68 kilograms (150 lb). The pelvis is narrower than in Homo sapiens, which is most likely for more efficient upright walking. This further indicates a fully terrestrial bipedalism, which is unlike older hominin species that show a combined feature of bipedalism and tree climbing. The Boy was relatively tall, which increased his body surface area that would enhance heat dissipation and prevent heat stress under the hot sun.

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. However, there are significant defining characters, such as bigger brain size (880 cc). The arms and legs are slightly longer indicating effective bipedality. The nose is projecting like those of humans rather than the open flat nose seen in apes. Body hair may also have been thinner (most likely naked) and possibly with increased sweat glands to hasten cooling. The skin also was most probably much darker with abundant melanin, as it was necessary to cope with the direct tropical sun rays in the African savannah.

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. Turkana Boy's thoracic vertebrae are narrower than in Homo sapiens. 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 exhalations of complex vocalisations.

Disease

It was suspected that Turkana Boy suffered from a congenital disorder, either of dwarfism or scoliosis. This was because the rib bones appeared asymmetrical to the spine and the reason was attributed to skeletal dysplasia. However, in 2013, a new study shows that, when the rib bones were carefully rearranged, it became symmetrical against the spine, and that an unusual structure of the vertebrae was characteristic of the early hominins. However, the fossil definitely showed lumbar disc herniation, an injury implicated with his death. He also had a diseased mandible.

See also

• List of human evolution fossils

References

• – Good popular level presentation
• – Technical papers

External links

• Media related to at Wikimedia Commons