Early Homo The earliest hominids humans walked bipedally Their brains were still ape size Even though they walked on two legs they could still climb trees better than us today How can we tell they are bipedal Cranial location of foramen magnum Postcranial shape of pelvis knee foot anatomy Hominids bipedal Earliest bipedal hominids from around 6 mya Four genera of interest to us 1 Ardipithecus 5 8 4 4 mya e Africa 2 Australopithecus 4 2 1 8 mya e and s Africa 3 Paranthropus 2 2 1 0 mya e Africa 4 Homo 2 5 mya to present Several candidates have been proposed for the first hominid dating as early as 7 mya in Africa I mentioned Salehanthropus 7 6 mya Chad But concentrated on Ardipithecus 5 8 4 4 mya east Africa Ardipithecus ramidus 4 4 mya Following Ardipithecus at least six species of Australopithecus Paranthropus Generally divided into two types Gracile Aus anamensis afarensis africanus sediba Robust P robustus P boisei A afarensis P boisei The gracile australopithecines are thought to have led to our genus Homo Early hominids Australopithecus gracile some thought to be our ancestors Paranthropus robust thought to be a separate lineage that went extinct P robustus P boisei robust A afarensis A africanus gracile Turnbaugh et al 2002 251 Artist John Gurche has reconstructed an Australopithecus afarensis face Australopithecus afarensis Stanford et al 2006 334 Postcranial comparisons Stanford et al 2006 330 At the end of the Pliocene between 3 0 1 7 mya we find several types of hominid Homo habilis 2 5 1 6 mya Paranthropus boisei robust 2 2 1 0 mya Paranthropus robustus robust 2 2 1 5 mya Australopithecus africanus gracile 3 0 2 3 mya Australopithecus sediba gracile 1 95 1 8 mya Homo first appears 2 5 mya in east and south Africa What led us to put this early hominid into our genus Two related items 1 Substantially larger brain 20 50 larger 2 First use of stone tools The first species of Homo appear between 3 2 mya They were reproductively isolated from the two species of robust hominids Paranthropus shown below Homo and Paranthropus co existed for 1 5 my after which the Paranthropus lineage disappeared forever 2 5 1 6 mya 3 9 3 0 mya A afarensis OR where does Aus sediba fit A africanus 3 0 2 3 mya P robustus 2 5 1 5 P boisei 2 2 1 0 mya Two scenarios now proposed 1 The older version has Australopithecus Homo habilis Homo erectus 3 9 2 3 mya 2 5 1 6 mya 1 8 mya 250 000 ya Which Australopithcus Previous slide showed Aus afarensis and possibly Aus africanus 3 9 3 0 mya 3 0 2 3 mya 2 Brand new hypothesis Australopithecus sediba Homo erectus 1 95 1 8 mya 1 8 mya 250 000 ya and Homo habilis either non existent or extinct What species to assign to particular fossils is not agreed upon These problems should clear up as more early Homo fossils are found Presently early Homo is found ONLY in Africa eastern and southern Most early Homo fossils are very fragmentary and scattered What sets Homo apart from Australopithecus The major difference is the first significant increase in BRAIN SIZE Smithsonian Institution A afarensis Homo habilis For comparative purposes brain size in cu cm or ml Modern human 1150 1750 x 1325 Homo habilis 500 800 x 680 20 50 bigger Australopithecus afarensis 400 500 x 440 10 bigger Ardipithecus ramidus 280 350 Modern chimp 285 500 x 390 There was some slight increase in brain size among australopithecines not as big as the jump in brain size we get with first Homo Homo habilis Found 2 5 1 6 mya at end of the Pliocene into Pleistocene in both east Africa and south Africa Face smaller less prognathous Hint of occipital torus First significant increase of brain size Vocabulary Occipital torus a ridge across the occipital bone at the back of the skull muscle attachment area Cranial characteristics Back teeth still large compared to us but smaller than earlier hominids the beginning of a general trend in humans toward smaller teeth Compared to Australopithecus 1 Larger cranial capacity beginning of trend 2 Less postorbital constriction 3 More rounded cranium no sagittal crest 4 Zygomatic arch smaller less massive jaw 5 Smaller slightly less prognathic face 6 Parabolic dental arch Australopithcus had Ushaped arch Homo habilis cranial characteristics Stanford et al 2006 354 A afarensis Not only is the brain bigger it is reorganized The left cerebral area developed more like ours right handedness language and ability to use symbols Larger brains generate more heat blood supply has double drain configuration that allows it to cool the brain Australopithecus also had this but Paranthropus had only one major drain This is called the Radiator Theory about why brain size could initially begin to expand very slightly among Australopithecines Larger brain size relative to body size Endocast cast of the inside of the skull Postcranial characteristics Basically the same as australopithecines except hands and feet are more modern Like A africanus long arms and short legs Still climbing trees as well as walking Rate of maturation faster than us today more like apes Still has a lot of sexual dimorphism more than today We see high variability in body size is it all male vs female Some early Homo are so much larger many paleoanthropologists are willing to consider them a separate species Homo rudolfensis from east Africa around what is now called Lake Turkana H habilis was about 4 5 ft tall H rudolfensis was 5 ft tall We will consider them all to be H habilis Homo rudolfensis H habilis to us Found in east Africa around 1 9 mya So far only one skull Elsewhere several thighbones may be H rudolfensis Thighbones indicate size of 5 ft tall and 144 lbs Large brain 752 ml less pronounced brow ridge and less prognathism Long face but also large molars Smithsonian Institution Homo habilis In other words we still have relatively few fossils of Homo habilis Disagreement over how variable H habilis is In this class we will lump the variability together into just one early Homo species H habilis When did language develop and what evidence could we see in the fossil record 1 Does vocal apparatus at basicranium allow speech Basicranium bones at base of skull 2 Do we see modern brain structure and organization Left hemisphere controls language and ability to use symbols 3 At what point did hominids have something to communicate about that would require language Modern chimp modern human 1 Basicranium anatomy modern human s allows greater range of sounds because basicranium is flexed Australopithecines do not
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