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10.3: Homo Habilis - The Earliest Members of Our Genus

  • Page ID
    191535
    • Bonnie Yoshida-Levine

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    Homo habilis has traditionally been considered the earliest species placed in the genus Homo. However, as we will see, there is substantial disagreement among paleoanthropologists about the fossils classified as Homo habilis, including whether they come from a single species or multiple, or even whether they should be part of the genus Homo at all.

    Homo habilis has a somewhat larger brain size—an average of 650 cubic centimeters (cc)—compared to Australopithecus with less than 500 cc. Additionally, the skull is more rounded and the face less prognathic. However, the postcranial remains show a body size and proportions similar to Australopithecus.

    Known dates for fossils identified as Homo habilis range from about 2.5 million years ago to 1.7 million years ago. Recently, a partial lower jaw dated to 2.8 million years from the site of Ledi-Gararu in Ethiopia has been tentatively identified as belonging to the genus Homo (Villmoare et al. 2015). If this classification holds up, it would push the origins of our genus back even further.

    Africa map with South Africa, Tanzania, Kenya, and Ethiopia shaded.
    Figure 10.4: Map showing major sites where Homo habilis fossils have been found. Ledi-Geraru is located in Ethiopia, Koobi Fora and Lake Turkana Basin are located in Kenya, the Olduvai Gorge is located in Tanzania, and Tuang, Malapa, Rising Star and Sterkfontein are located in South Africa. Credit: Homo habilis site map (Figure 10.4) original to Explorations: An Open Invitation to Biological Anthropology by Chelsea Barron at GeoPlace, California State University, Chico is under a CC BY-NC 4.0 License.

    Discovery and Naming

    The first fossils to be named Homo habilis were discovered at the site of Olduvai Gorge in Tanzania, East Africa, by members of a team led by Louis and Mary Leakey (Figure 10.4). The Leakey family had been conducting fieldwork in the area since the 1930s and had discovered other hominin fossils at the site, such as the robust Paranthropos boisei. The key specimen, a juvenile individual, was actually found by their 20-year-old son Jonathan Leakey. Louis Leakey invited South African paleoanthropologist Philip Tobias and British anatomist John Napier to reconstruct and analyze the remains. The fossil of the juvenile shown in Figure 10.5 (now known as OH-7) consisted of a lower jaw, parts of the parietal bones of the skull, and some hand and finger bones. The fossil was dated by potassium-argon dating to about 1.75 million years. In 1964, the team published their findings in the scientific journal Nature (Leakey et al. 1964). As described in the publication, the new fossils had smaller molar teeth that were less “bulgy” than australopithecine teeth. Although the primary specimen was not yet fully grown, an estimate of its anticipated adult brain size would make it somewhat larger-brained than australopithecines such as Austalopithecus africanus. The hand bones were capable of a precision grip like a human’s hand. This increased the likelihood that stone tools found earlier at Olduvai Gorge were made by this group of hominins. Based on these findings, the authors inferred that it was a new species that should be classified in the genus Homo. They gave it the name Homo habilis, meaning “handy” or “skilled.”

    Two lateral right views of skulls and a jaw with blackened teeth.
    Figure 10.5a-c: Homo habilis fossil specimens. From left to right they are: a. lateral right view of OH-24 (found at Olduvai Gorge), b. lateral right view of KNM-ER-1813 (from Koobi Fora, Kenya), and c. the jaw of OH-7, which was the type specimen found in 1960 at Olduvai Gorge, Tanzania. Credit: a. Homo habilis: OH 24 lateral right view by ©eFossils is under a CC BY-NC-SA 2.0 License and is used as outlined by eFossils. b. Homo habilis: KNM-ER 1813 lateral right view by ©eFossils is under a CC BY-NC-SA 2.0 License and is used as outlined by eFossils. c. Homo habilis OH 7 Jaw by ©BoneClones is used by permission and available here under a CC BY-NC 4.0 License.

    Controversies over Classification of Homo habilis

    Since its initial discovery, many more Homo habilis were discovered in East and South African sites during the 1970s and 1980s (Figure 10.6). As more fossils joined the ranks of Homo habilis, several trends became apparent. First, the fossils were quite variable. While some resembled the fossil specimen first published by Leakey and colleagues, others had larger cranial capacity and tooth size. A well-preserved fossil skull from East Lake Turkana labeled KNM-ER-1470 displayed a larger cranial size along with a strikingly wide face. The diversity of the Homo habilis fossils prompted some scientists to question whether they displayed too much variation to all belong to the same species. They proposed splitting the fossils into at least two groups. The first group resembling the original small-brained specimen would retain the species name Homo habilis; the second group consisting of the larger-brained fossils such as KNM-ER-1470 would be assigned the new name of Homo rudolfensis (see Figure 10.7). Researchers who favored keeping all fossils in Homo habilis argued that sexual dimorphism, adaptation to local environments, or developmental plasticity could be the cause of the differences. For example, modern human body size and body proportions are influenced by variations in climates and nutritional circumstances.

    Figure 10.6: Key Homo habilis fossil locations and the corresponding fossils and dates. Credit: Homo habilis table (Figure 10.6) original to Explorations: An Open Invitation to Biological Anthropology by Bonnie Yoshida-Levine is under a CC BY-NC 4.0 License.
    Location of Fossils Dates

    Description

    Ledi-Gararu, Ethiopia 2.8 mya Partial lower jaw with evidence of both Australopithecus and Homo traits; tentatively considered oldest Early Homo fossil evidence.
    Olduvai Gorge, Tanzania 1.7 mya to 1.8 mya Several different specimens classified as Homo habilis, including the type specimen found by Leakey, a relatively complete foot, and a skull with a cranial capacity of about 600 cc.
    Koobi Fora, Lake Turkana Basin, Kenya 1.9 mya Several fossils from the Lake Turkana basin show considerable size differences, leading some anthropologists to classify the larger specimen (KNM-ER-1470) as a separate species, Homo rudolfensis.
    Sterkfontein and other possible South African cave sites about 1.7 mya South African caves have yielded fragmentary remains identified as Homo habilis, but secure dates and specifics about the fossils are lacking.
         
    Front view of black and white skull, missing lower jawbone.
    Figure 10.7: Cast of the Homo habilis cranium KNM-ER-1470. This cranium has a wide, flat face, larger brain size, and larger teeth than other Homo habilis fossils, leading some scientists to give it a separate species name, Homo rudolfensis. Credit: Homo rudolfensis Cranium KNM-ER 1470 by ©BoneClones is used by permission and available here under a CC BY-NC 4.0 License.

    Given the incomplete and fragmentary fossil record from this time period, it is not surprising that classification has proved contentious. As a scholarly consensus has not yet emerged on the classification status of early Homo, this chapter makes use of the single (inclusive) Homo habilis species designation.

    There is also disagreement on whether Homo habilis legitimately belongs in the genus Homo. Most of the fossils first classified as Homo habilis were skulls and teeth. When arm, leg, and foot bones were later found, making it possible to estimate body size, the specimens turned out to be quite small in stature with long arms and short legs. Analysis of the relative strength of limb bones suggested that the species, though bipedal, was much more adapted to arboreal climbing than Homo erectus and Homo sapiens (Ruff 2009). This has prompted some scientists to assert that Homo habilis behaved more like an australopithecine—with a shorter gait and the ability to move around in the trees (Wood and Collard 1999). They were also skeptical of the claim that the brain size of Homo habilis was much larger than that of Australopithecus. They have proposed reclassifying some or all of the Homo habilis fossils into the genus Australopithecus, or even placing them into a newly created genus (Wood 2014).

    Other scholars have interpreted the fossil evidence differently. A recent reanalysis of Homo habilis/rudolfensis fossils concluded that they sort into the genus Homo rather than Australopithecus (see Hominin Species Summaries at chapter end). In particular, statistical analysis performed indicates that the Homo habilis fossils differ significantly in average cranial capacity from the australopithecines. They also note that some australopithecine species such as the recently discovered Australopithecus sediba have relatively long legs, so body size may not have been as significant as brain- and tooth-size differences (Anton et al. 2014).

    Special Topic: Kamoya Kimeu

    Kamoya Kimeu (1938–2022) is arguably the most prolific fossil hunter in the history of paleoanthropology (Figure 10.8). In addition to his many decades of work as a field excavator and project supervisor in East Africa, he also trained field workers and scholars and has served as curator for prehistoric sites for the National Museum of Kenya.

    Man smiling at camera with lake and mountain in the background.
    Figure 10.8: Kamoya Kimeu (1938-2022). Credit: Photograph of Kamoya Kimeu by ©Dr. Mark Teaford is used by permission.

    Kamoya Kimeu was born in 1938 in rural southeastern Kenya. Despite a formal education that did not go past the sixth grade, he had an aptitude for languages and familiarity with the plants and animals in the East African bush that led him to a job in Tanzania as a field excavator for Louis and Mary Leakey in 1960. In the years that followed, Kimeu found dozens of major hominin fossils. These included a Paranthropus boisei mandible at Olduvai Gorge, Homo habilis specimen KNM-ER-1813 from the Turkana Basin (shown in Figure 10.5), and a key early modern Homo sapiens fossil from the Omo Valley, Ethiopia. Kimeu’s most famous fossil discovery was the skeleton of a young Homo erectus by the Nariokotome river bed in 1984. This finding was highly significant because it was a nearly complete early hominin skeleton and provided insight into child development within this species. In recognition of his work, Kimeu was awarded the National Geographic Society La Gorce Medal by U.S. President Ronald Reagan in 1985.

    Traditionally, there has been a divide between African field workers and foreign research scientists, who would typically conduct seasonal field work in Africa, then travel back to their home institutions to publish their findings. Although Kimeu received widespread acclaim for the Nariokotome discovery, as well as a personal acknowledgement in the publication of the find in the journal Nature, he was not credited as an author. More recently, Kimeu’s intellectual contributions to the field of paleoanthropology have been recognized. In 2021, he received an honorary doctorate degree from Case Western Reserve University in Ohio. Kimeu’s most lasting legacy may be his mentorship of countless field workers and students. Today, there are a small but growing number of Black African paleoanthropologists taking on principal roles in the science of human origins.


    This page titled 10.3: Homo Habilis - The Earliest Members of Our Genus is shared under a CC BY-NC 4.0 license and was authored, remixed, and/or curated by Bonnie Yoshida-Levine (Society for Anthropology in Community Colleges) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.