Homo ergaster—KNM-WT 15000
Fossil Item Type Metadata
Specimen/Species Time Range
Specimen Data (Morphology)
KNM-WT 15000 is one of the most complete hominid fossils discovered. His discovery at the Turkana site in Kenya designated the nickname “Turkana Boy.” Turkana Boy stands approximately 162.56 cm (5.3 feet), and at first glance, may resemble an adult hominid. However, the unfused epiphyses and unerupted third molars indicate Turkana Boy was a juvenile, approximately 11 to 12 years of age. Assuming Turkana Boy was not subject to growth irregularities, H. ergaster would have been significantly larger than any previously existing hominid. As the most complete specimen of his species, Turkana Boy provides growth trajectory data for the postulated developmental pattern H. ergaster most likely followed.
Turkana Boy’s morphologies indicate he lived in a hot and arid climate consistent with the Turkana region, based on his thin, elongated torso and long limbs designed to dissipate the heat,. Also consistent with the thermoregulatory theory is Turkana Boy’s wide nasal aperture, designed for inhaling deeply in the arid climate. His non-flaring zygomatic bones would also be consistent with protecting the face from intense UV rays. Cranially, Turkana Boy exhibits many features similar to modern Homo sapiens, such as projecting nasal bones and an increased cranial capacity. However, there are many differences as well. Turkana Boy exhibits a long and low cranial vault, whereas modern humans have a tall, and shortened cranial vault. Turkana Boy also has a low sloping forehead, strong brow ridge, and is an absent chin—all features present in modern humans. The wide cranial breadth and standard supraorbital sulcus behind the supraorbital torus relate more closely to H. erectus specimens and differs from other H. ergaster specimens, possibly due to his juvenile status. The dentition is greatly reduced in size compared to previously existing hominids, as well as smaller areas for masticatory muscle attachments, suggesting a softer diet.
Postcranially, Turkana Boy exhibits an array of morphologies that relate very closely to modern H. sapiens. Significantly, Turkana Boy stands at a height similar to modern equatorial African natives, with limb proportions resembling their own. However, there are morphologies that set them vastly apart. The spinal column is longer than moderns and shows less curvature with spinal cord constriction that would have limited nerve signaling to the thoracic cavity, possibly rendering the H ergaster speechless (again, suggesting no growth irregularities). While he exhibits many traits ancestral to modern humans, Turkana Boy actually represents a greater capability for high-speed bipedal locomotion. Turkana Boy displays a much narrower, taller pelvis than modern humans, allowing for more efficient locomotion.
- Date Added
- March 21, 2017
- Early Homo Group 2
- Item Type
- “Homo ergaster—KNM-WT 15000,” Hominid Fossil Repository, accessed February 19, 2020, http://projects.leadr.msu.edu/hominidfossils/items/show/17.