The History of Our Tribe Hominini Textbook Part IV Pleistocene Epoch Chapter 28 Homo ergaster

28 . Homo Homo ( human I working man ) Figure of Homo . Homo erectus new by . is licensed under . SITES Algeria Morocco Thomas Quarries and Sidi 165 Ethiopia and Kenya and Gorge South Africa possibly PEOPLE Richard , Bernard INTRODUCTION As mentioned , the African form of the erectus grade is termed Homo . PHYLOGENY is thought to have evolved from either habilis or in East Africa . However , it is possible that habilis may have been the first to leave Africa , after which it may have evolved into a form that then moved into Africa and Asia . If habilis was in our ancestry , the ter scenario might explain how the more modernly proportioned appeared in the fossil record contemporary with habilis in East Africa . Of course , the hit and miss nature of the fossil record and fossil and species discoveries could also explain that phenomenon , the seeming lack of transitional forms in Africa . DISCOVERY AND GEOGRAPHIC RANGE The earliest material is from the East Lake site of Fora in Kenya . Richard is credited with this discovery . Other sites outside of Africa are contemporary with African sites , eg . the site in the Republic of Georgia and the site of in Java . Note There are problems with the Javanese dates because the layers are not conducive to more reliable dating methods . The almost complete or Boy ( see Figure ) from the West Lake region of Kenya was discovered in 1984 by and dated to . The ton has been extremely important for reconstructing body morphology and limb proportions . The boy is thought to have been eight years old based upon tooth development patterns . He was formerly thought to be as old as 15 , based on his height , stage of bone development , and hypothesized growth trajectories . ever , dental calculations can accurately determine age due to the daily pattern of enamel deposition during tooth development . Scientists can count the microscopic , deposits that are laid down daily ing the course of a tooth development . Once it was determined that he was only eight years old yet ' tall , it was apparent that developed at a much faster rate , more like a chimp than a human . Had Boy lived to adulthood , he would have been over ' tall . His morphology was adapted to the hot , dry conditions in equatorial East Africa , tall and , similar to modern peoples of the region . Other African sites include the North African sites of ( formerly and sometimes assigned to Home ) in Algeria and Thomas Quarries and Sidi in Morocco the East African 166 The History of Our Tribe

sites of and in Ethiopia , in Kenya , and Gorge in and possibly the South African site of , although it is not universally accepted that was there . Figure Bo by Mike Peel is licensed under . PHYSICAL CHARACTERISTICS exhibited robust craniofacial characteristics relative to modern humans , but overall we see the continued reduction in dentition and masticatory apparatus . Their brains were large , with a maximum capacity of 1200 and a range of , based on the material from the three continents . ever , the relative brain size of early specimens may not have been much greater than that seen in early Homo . They had fairly robust supraorbital and nuchal regions . The skull vault was long and low , termed platycephalic , with a low maximum width . Our vaults are much higher , and we have high maximum width , due to subsequent cerebral expansion . The shape of the vault in has been described as that of a turtle shell . like all before and especially the robust , exhibits constriction between the orbits and the cranial vault . Their temporal lines were more pronounced than ours ( see Figure ) indicating that they had more powerful jaw muscles and chewing capabilities . They did not have much of a forehead due to several of the aforementioned craniofacial characteristics . Their nasal bones suggest a , projecting nose . This would have been adaptive in arid as well as cold conditions . In addition to warming and inhaled air , the moisture in warm exhaled air condenses on the cooler nasal membranes , resulting in water conservation . The jaws were somewhat prognathic in the alveolar region , ie . the bone that houses the teeth , and the mandibles were robust . They lacked a chin , a characteristic seen only in anatomically modern humans . Relative to habilis , long thought to be the species from which was derived , a longer skull vault , a larger brain ( however , see previous paragraph ) a smaller temporal fossa ( the opening formed by the zygomatic arch where jaw muscles pass through attach ) a shorter face , a larger nose , reduced dentition and jaw robusticity , and a heavier nuchal region . 28 . Homo 167

Figure Homo by Taylor . Relative to Asian , possessed a higher cranial vault , and the bones of the vault were thinner . They also did not exhibit the sagittal keel ( see Homo erectus , Chapter 29 ) typical of the Asian form . However , the Fora specimen exhibits slight keeling ( see Figure ) erg was very . While the thorax may still have been somewhat conical , they had more of a waist , demonstrating an uncoupling of the lower limb from the torso . The small birth canal relative to adult brain size suggests a long period of postnatal brain growth , as seen in subsequent , especially our own species . They were tall , achieving heights of over ' They were also more robust than premodern humans that , in turn , were more robust than modern humans . Males were larger than females . While the lifespan tended to be short , some individuals lived to be 50 to 60 years of age . There was high infant mortality , with 40 of fossil remains estimated to be less than 14 years of age . 168 The History of Our Tribe

Figure Fom Homo . Postorbital constriction . Slight healing Temporal line . Homo skull replica World Museum by is licensed under BY Review of Primitive Characteristics Retain Initially brain possibly no larger than early Homo Some robusticity in cranium and face . Supraorbital and nuchal tori . Postorbital constriction . Low forehead . Conical thorax . Relative to later Platycephalic skull vault with low maximum breadth . Pronounced temporal lines . Alveolar prognathism . Large teeth but smaller than previous species . No chin . 28 . Homo 169

Review of Derived Characteristics Protruding nose . robust . Tall with long legs . Development of waist ( decoupling between torso and lower limb ) ENVIRONMENT AND WAY OF LIFE The environment of East Africa during the was hot and arid . Savannas had expanded and forests had become increasingly fragmented . There was increased volcanic activity in the Great Rift zone , and that is one hypothesis as to why at least a portion of the population moved out of the area . It is of great est as to how and why ( or a predecessor ) first left East Africa . The how is not as difficult as the While they may have crossed the Red Sea , they could also have come up through the Nile Valley and exited Africa across the Arabian land bridge that was exposed at the time . As to why they left , there are a variety of ideas that are not mutually exclusive . They may have ventured farther and farther due to ( competition for resources with their own or other species of or ( local resource depletion ( similar environment ( there is speculation that they were a grassland species that followed African grasslands into West Asian steppes , through the Indian subcontinent , and southeast to Indonesia ) following herd animals north and out of Africa or ( the aforementioned volcanic activity . While there is debate as to whether the various erectus species hunted large game , it is not likely , since they lacked weaponry . It is generally accepted that they were mobile scavengers and that hunted opportunistically . They certainly would have been capable of taking small prey and older or injured animals . Faunal remains at the , China , site consisted of deer , elephant , rhino , and beaver remains , but the bulk of the animal matter in their diet is thought to have come from smaller animals , such as rodents , hedgehogs , hares , and frogs , as well as ostrich eggs . However , and ( 2014 ) have faunal remains at the site in Gorge , and concluded that the high percentage ( 72 ) of large prey ( especially with weights of ) conforms solely to hunting patterns , versus accidental deaths or carnivore kills . Thus at least some are thought to have been practicing ambush hunting and were therefore hunters . While nomadic , they are thought to have stayed in an area for at least short periods of time , relative to past species . Early is associated with the technology , and that is the technology that they took with them out of Africa . subsequently invented a tool tradition , termed , that first appears in the archaeological record at ( newer data suggests possibly as early as ) and lasted to as late as 115 kya in some areas . The latter industry spread throughout Africa and as far east as the Indian subcontinent and west to Western Europe . It involved the use of better stone resources and tools that were more refined and standardized than in the tradition . The most representative tool was a worked ( shaped on both sides ) hand axe in the shape of a teardrop ( see Figure ) The tool manifests what is called a target design , in that the manufacturer knew what he or she was making and followed standardized steps in shaping the core into the resulting tool form . Once the core was prepared with the use of a stone hammer , the next step involved a soft hammer technique ( see Figure ) This required the use of a bone or antler hammer that could more carefully control the size and shape of the to be removed on either side of the axe as it was shaped . Sharper and straighter edges resulted from the . The had different tools for different purposes . The categories of tools included hand axes , 170 The History of Our Tribe

Figure hand axe . en mano by Jose Alvarez is licensed under smaller tools , choppers , picks , cleavers , and some bone tools . They would likely have been used to kill butcher scrape and cut hides shape wood , bone , antler , and stone and harvest and process plant foods . Figure Soft hammer percussion . Hammer by is in the public domain . 28 . Home 171

It would have been necessary for erectus to have had some sort of body covering prior to moving north into colder regions of . There is some evidence to support use of fire , but it is scant . However , even in later species wherein we know they had fire , such as and , there are fewer hearths apparent at archaeological sites than would be expected . It was previously believed that the erectus grade lacked the technology to cross open water and therefore were limited to land travel . However , the discovery of a site dated to kya on the island of Flores suggests that early erectus were capable of crossing fairly sizeable stretches of open sea . It is thus possible that may have across the Red Sea to the Arabian Peninsula or across the Mediterranean to or Italy ( via Sicily ) during periods of lower sea levels when much of the earth water was tied up in ice . While it is likely that and related species had some complex form of communication , due to their advanced cultural achievements , it is not known whether they had speech or language similar to our own . They possessed the arched palate , flexed cranial base , and cerebral centers that are necessary for speech production and comprehension . However , Boy had small intervertebral ( the openings in between the vertebrae where the spinal nerves exit the spinal cord ) in the thoracic region . It is thus thought that they may not have had the necessary motor function for controlled breathing and speech . However as mentioned in the section on Homo ( Chapter 23 ) I believe the standardized nature of the tool industry demonstrates active teaching and thus theory of mind that in turn assumes some sort of . 172 The History of Our Tribe