The Turkana Human, formally known as KNM-WT 15000, is one of the most complete early human skeletons ever discovered. This fossil provides insights into the evolutionary journey of our ancestors. Its preservation offers a window into the physical characteristics, growth patterns, and way of life of early hominins.
Discovery and Initial Findings
The discovery of the Turkana Human fossil occurred in 1984 near Lake Turkana in Kenya, on the bank of the Nariokotome River. Kamoya Kimeu, a member of a team led by paleoanthropologists Richard Leakey and Alan Walker, made this find. The skeleton’s exceptional completeness, comprising approximately 90% of the bones, was a major scientific event.
The skeleton’s extensive preservation allowed scientists to gather much data about an early human. Unlike many fragmented hominin finds, the Turkana Human offered a comprehensive view of an ancient individual’s anatomy. This completeness made it possible to reconstruct body proportions and growth patterns accurately, providing a clearer picture of our evolutionary past.
Physical Characteristics and Estimated Age
The Turkana Human was a young male, estimated to be between 8 and 12 years old at the time of his death. Scientists determined his age by analyzing dental development, specifically the eruption of his second molars but not his third molars. Bone growth patterns and microscopic analysis of tooth enamel deposition also helped pinpoint his age.
At his death, the Turkana Human stood approximately 5 feet 3 inches (1.6 meters) tall and weighed about 106 pounds (48 kg). Studies suggest that if he had reached adulthood, he might have grown to around 5 feet 9 inches to 6 feet 1 inch (1.75 to 1.85 meters) and weighed about 150 pounds (68 kg), indicating a potential adolescent growth spurt similar to modern humans. His build was slender, and his brain size was approximately 880 cubic centimeters, with an estimated adult capacity of around 909 cubic centimeters. This is considerably smaller than the average modern human brain, which is about 1350 cubic centimeters.
The fossil is dated to approximately 1.5 to 1.6 million years ago, based on geological dating of the sediments where it was found. The skeletal structure displayed a mix of features, including a low, sloping forehead, pronounced brow ridges, and the absence of a chin, not seen in Homo sapiens. His long legs and narrow shoulders were adaptations beneficial for living in a hot, dry climate, similar to some modern human populations.
Evolutionary Significance
The Turkana Human is classified as Homo ergaster, a species often considered an early African form of Homo erectus. This classification is important because Homo ergaster is believed to be a direct ancestor of later hominins, including Homo sapiens. The nearly complete skeleton provided scientists with insights into the body proportions and growth patterns of early Homo, previously unknown from more fragmentary remains.
The skeleton demonstrated a shift towards modern human-like body proportions, characterized by long legs and a more upright posture, adapted for efficient bipedalism. This anatomical configuration suggests adaptation for long-distance walking and endurance running, enabling these early humans to cover vast distances in search of food and water. The narrow pelvis, compared to Homo sapiens, further supports this adaptation for efficient upright locomotion.
Understanding the growth patterns of the Turkana Human has also been insightful. While initial analyses suggested a growth rate similar to modern humans, further research indicates that Homo ergaster likely matured faster than Homo sapiens but slower than chimpanzees. This intermediate growth rate suggests a longer childhood period than earlier hominins, which could imply more complex social structures and extended learning opportunities for the young.
Inferred Lifestyle and Environment
Based on analysis of the Turkana Human and its archaeological context, scientists infer aspects of its daily life and environment. The anatomy of Homo ergaster, particularly its adaptations for long-distance walking and running, suggests a mobile, terrestrial lifestyle. This mobility would have been advantageous for a hunter-gatherer existence, allowing them to follow migrating animal herds and exploit varied food resources.
The diet of Homo ergaster was likely omnivorous, incorporating both plant matter and meat. While no tools were found directly with the skeleton, Homo ergaster is associated with the Acheulean tool industry, characterized by distinctive oval and pear-shaped bifacial handaxes. These stone tools would have been used for tasks including butchering animals, processing plants, and possibly digging.
The Turkana Basin, where the fossil was found, was a dynamic environment approximately 1.5 to 1.6 million years ago. While today it is largely an arid, semi-desert region, evidence suggests that during the early Pleistocene, it featured a mosaic of savanna grasslands, woodlands, and areas around a larger lake. This varied landscape would have supported diverse animal life, including grazing animals like antelopes, hippos, baboons, and extinct elephants, providing resources for early human populations.