University of Rhode Island DigitalCommons@URI Sociology & Anthropology Faculty Publications Sociology & Anthropology 2010 Origin of the Genus Homo Holly M. Dunsworth University of Rhode Island, [email protected] Creative Commons License This work is licensed under a Creative Commons Attribution 3.0 License. Follow this and additional works at: https://digitalcommons.uri.edu/soc_facpubs Citation/Publisher Attribution Dunsworth, Holly M. "Origin of the genus Homo." Evolution: Education and Outreach, vol. 3, no. 3, 2010, pp. 353-366. http://www.dx.doi.org./10.1007/s12052-010-0247-8 Available at: http://www.dx.doi.org./10.1007/s12052-010-0247-8 This Article is brought to you for free and open access by the Sociology & Anthropology at DigitalCommons@URI. It has been accepted for inclusion in Sociology & Anthropology Faculty Publications by an authorized administrator of DigitalCommons@URI. For more information, please contact [email protected]. Evo Edu Outreach (2010) 3:353–366 DOI 10.1007/s12052-010-0247-8 ORIGINAL SCIENTIFIC ARTICLE Origin of the Genus Homo Holly M. Dunsworth Published online: 11 August 2010 # Springer Science+Business Media, LLC 2010 Abstract The origin of the genus Homo in Africa signals trends, canine reduction and postcranial metamorphosis in the beginning of the shift from increasingly bipedal apes to the following genera: Sahelanthropus, Orrorin, Ardipithe- primitive, large-brained, stone tool-making, meat-eaters that cus, Australopithecus, and Paranthropus. As the Pliocene traveled far and wide. This early part of the human genus is epoch came to a close and global climate was shifting at represented by three species: Homo habilis, Homo rudol- about 2.5 million years ago (deMenocal 2004), there is a fensis, and Homo erectus. H. habilis is known for retaining concomitant change in the hominin fossil record. In this primitive features that link it to australopiths and for being increasingly cooler world, something new, both anatomi- the first stone tool makers. Little is known about H. cally and behaviorally, emerged. This is the origin of the rudolfensis except that it had a relatively large brain and genus Homo. large teeth compared to H. habilis and that it overlapped in Of the earliest members of the genus Homo, the best- time and space with other early Homo. Our understanding known species are Homo habilis, Homo rudolfensis, and of the paleobiology and evolution of the larger-brained H. Homo erectus (Table 1). Listed roughly in order of their erectus is enhanced due to its rich fossil record. H. erectus earliest appearance from oldest to youngest, these three was the first obligate, fully committed biped, and with a species are the focus of this review. The first two species body adapted for modern striding locomotion, it was also are the most primitive. Compared to what is known about the first in the human lineage to disperse outside of Africa. H. erectus, little is known about how they differ in anatomy The early members of the genus Homo are the first to tip and behavior from one another and from preceding the scale from the more apish side of our evolutionary australopiths. Although it was anatomically and behavior- history toward the more human one. ally primitive compared to modern humans, H. erectus signifies a major shift in hominin evolution, most notably Keywords Paleoanthropology. Homo . H. habilis . through increased brain and body size and increasingly H. rudolfensis . H. erectus . Pleistocene . Oldowan . complex tools and behaviors. Acheulean . Bipedalism . Encephalization It is generally agreed upon that H. habilis, spanning from 2.3 to 1.4 million years ago, is descended from a species of Australopithecus.IfH. habilis evolved in East Africa, then Introduction Australopithecus afarensis and Australopithecus garhi are its possible ancestors, but if H. habilis evolved in South For the first, four million years or so of hominin evolution, Africa, then Australopithecus africanus and Australopithe- the hominin fossil record is characterized by, among other cus sediba are candidates. Future fossil discoveries will probably answer this question. However, based on what is already known about H. habilis, it widely accepted that it is H. M. Dunsworth (*) the common ancestor of all later species in the genus Homo Department of Anthropology, Northeastern Illinois University, including our own, Homo sapiens. 5500 N St. Louis Ave, — Chicago, IL 60625, USA H. habilis and H. rudolfensis the poorly understood, but e-mail: [email protected] slightly larger species dated to about 1.9 million years ago 354 Evo Edu Outreach (2010) 3:353–366 (Fig. 1)—arerestrictedtoEastandSouthAfrica.However, H. erectus, which diverged from H. habilis around 1.8 million years ago, marks the first hominin to disperse outside of Africa. Between about 1.9 and 1.8 million years ago, there is evidence for geographic and temporal overlap of all three early Homo species in East Africa. The exceptionally large-toothed and strong-jawed robust australopiths (Paranthropus, which also descended from an earlier Australopithecus species), with their distinct dietary niche, one of tough nuts, seeds and fruits and fibrous vegetation, continued to thrive in some of the same localities as these species of early Homo, but they remained evolutionarily separate. Early Homo is distinguishable from contemporaneous robust australopiths by their smaller Trinil, Java, Indonesia; Zhoukoudian,and Hexian, Gongwangling, Nanjing, China; Narmada,Georgia; India; Salé, Dmanisi, Morocco; Buia,Awash, Eritrea; Ethiopia; Daka, Ileret, Middle KoobiWest Fora, Turkana, Olorgesailie, Kenya; and OlduvaiSterkfontein Gorge, and Tanzania; Swartkrans, South Africa Gorge, Tanzania; Drimolen, Sterkfontein,Swartkrans, and South Africa teeth and jaws and by larger cranial capacity. Omo, Ethiopia; Ileret and Koobi Fora, Kenya; Olduvai Koobi Fora, Kenya; Uraha, Malawi Mojokerto, Ngandong, Sambungmachan, Sangiran, and Because it is more derived, H. erectus is more easily distinguished from earlier hominins and Paranthropus— ; not just in craniodental anatomy but in body proportions ; ; and postcranial morphology as well. H. erectus is nearly modern in its postcranial anatomy, with few exceptions. Homo ; Within Africa, early H. erectus overlapped with the two other species of early Homo but eventually far outlasted habilis rudolfensis Australopithecus rudolfensis Homo georgicus Homo erectus sensu stricto Australopithecus Homo habilis Homo ergaster them. Outside of Africa, H. erectus fossils are the most primitive hominins yet discovered, and remains have been recovered from sites across Eurasia and Indonesia, beginning as early as about 1.8 million years ago and spanning over one million years, disappearing in Asia by about 400 thousand years ago (Shen et al. 2009). It is possible that the last H. erectus may have survived in Indonesia as recently as 30,000 years ago (Swisher et al. 1996), after H. sapiens had already reached the region, but this date is controversial and may be soon replaced by a much older estimate of about 550,000 years ago (Indriati et al. 2010). Regardless of its extinction date, H. erectus KNM-ER 42703 (maxilla); OHhand); 7 OH (type; 8 parts (foot); ofOH OH skull, 62 16 (partial (cranium); skeleton); OHSK OH 24 847 65 (cranium); (cranium) (maxilla); Ngandong 13 (cranial vault);Sangiran Sangiran 17 2 (cranium); (cranial Trinil vault); Zhoukoudian 2 XII (type; (calvaria); skullcap); D2280D2700 (calvaria); (cranium); D2282 D3444 (cranium); (cranium);KNM-ER KNM-ER 1481 992 (femur); (mandible); KNM-ERKNM-ER 3733 3883 (cranium); (cranium); KNM-ERKNM-OG 42700 45500 (cranial (cranial vault); vault);OH KNM-WT 9 15000 (cranial (skeleton); vault); OH 28 (partial pelvis) Key specimens Alternative taxonomy Key sites 1.4 KNM-ER 1805 (cranium); KNM-ER 1813 (cranium); 0.4 Perning 1 (calvaria); Ngandong 7 (cranial vault); – – years ago 2.4 1.91.8 KNM-ER 1470 (type; cranium); UR 501 (mandible) Homo Early genus Fig. 1 Both found in the early 1970s at sites at Koobi Fora, Kenya, these skulls, from left to right, of H. habilis (KNM-ER 1813) and H. rudolfensis (KNM-ER 1470) represent the variation in size exhibited Table 1 SpeciesHomo habilis Millions of Homo rudolfensis Homo erectus by early Homo. Photographs by Alan Walker Evo Edu Outreach (2010) 3:353–366 355 thrived and evolved across the tropical and temperate dated to about 2.4–2.0 million years ago; (g) a partial regions of the Old World with a much wider geographic cranium with teeth (attributed to A. garhi; Asfaw et al. distribution than any preceding hominins. 1999) and associated limb bones from the Hata Member, As with so many mammalian extinctions in the Bouri Formation of Ethiopia, dated to about 2.5 million Pleistocene fossil record, it is unclear why H. erectus did years ago. not survive to the present day, except that later species of Another candidate for earliest Homo has recently been Homo had much bigger brains, much more sophisticated announced. The remains of two partial skeletons from technology, and either indirectly or directly out-competed Malapa, South Africa, dated to 1.9 million years ago, have H. erectus at being big-brained, bipedal, stone tool-making been attributed to A. sediba (Berger et al. 2010), but their hominins. Homo-like traits (e.g., small premolars and molars and Because the fossil record is denser for this species, the derived bipedal traits in the pelvis and legs) beckon variation in H. erectus is better understood than in any of researchers to test the hypotheses that these finds belong the earlier hominins. A growing proportion of researchers either to the ancestor of Homo or to the genus Homo. employ a separate species name for the earliest members None of the candidates for earliest Homo lands firmly in of H. erectus that tend to be smaller and are found mostly the known range of anatomical variation for H. habilis, H. inAfrica;theycalltheseHomo ergaster (Tattersall 2007; rudolfensis,orH. erectus. However, they all show arguable for discussion see Dunsworth and Walker 2002).