PowerPoint PresentationSlide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Early HomoThe earliest hominids (humans) walked bipedallyTheir brains were still ape-sizeEven though they walked on two legs, they could still climb trees better than us todayHow can we tell they are bipedal?Cranial: location of foramen magnumPostcranial: shape of pelvis, knee, foot anatomyHominids (bipedal)Earliest bipedal hominids from around 6 myaFour genera of interest to us:1. Ardipithecus 5.8-4.4 mya, e Africa2. Australopithecus 4.2-1.8 mya, e and s Africa3. Paranthropus 2.2-1.0 mya, e Africa4. Homo 2.5 mya to presentSeveral candidates have been proposed for the firsthominid, dating as early as 7 mya in AfricaI mentioned Salehanthropus, 7-6 mya, ChadBut concentrated on Ardipithecus, 5.8-4.4 mya, east AfricaArdipithecusramidus4.4 myaFollowing Ardipithecus,at least six species of Australopithecus/ParanthropusGenerally divided into two types:Gracile: Aus. anamensis, afarensis, africanus, sedibaRobust: P. robustus, P. boiseiThe gracile australopithecines are thought to have ledto our genus, HomoA. afarensisP. boiseiEarly hominidsAustralopithecus (gracile), some thought to be our ancestorsParanthropus (robust), thought to be a separate lineage that went extinct(Turnbaugh et al. 2002:251)A. africanusA. afarensisP. boiseiP. robustusrobustgracileArtist John Gurche has reconstructedan Australopithecus afarensis faceAustralopithecus afarensis(Stanford et al. 2006:334)(Stanford et al. 2006:330)Postcranial comparisonsAt the end of the Pliocene, between 3.0-1.7 myawe find several types of hominid:Australopithecus africanus (gracile) (3.0-2.3 mya)Australopithecus sediba (gracile) (1.95-1.8 mya)Paranthropus boisei (robust) (2.2-1.0 mya)Paranthropus robustus (robust) (2.2-1.5 mya)Homo habilis (2.5-1.6 mya)Homo first appears 2.5 myain east and south AfricaWhat led us to put this early hominid into our genus?Two related items:1. Substantially larger brain, 20-50% larger2. First use of stone toolsThe 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 forever2.5-1.5 mya2.2-1.0 mya 3.0-2.3 mya2.5-1.6 mya3.9-3.0 myaP. robustusP. boiseiA. africanus A afarensis ?OR where doesAus. sediba fit???Two scenarios now proposed:1. The older version hasAustralopithecus – Homo habilis – Homo erectus 3.9-2.3 mya 2.5-1.6 mya 1.8 mya – 250,000 yaWhich Australopithcus??? Previous slide showedAus. afarensis, and possibly Aus. africanus 3.9-3.0 mya 3.0-2.3 mya2. Brand new hypothesis:Australopithecus sediba – Homo erectus 1.95-1.8 mya 1.8 mya – 250,000 yaand Homo habilis either non-existent, or extinctWhat species to assign to particular fossilsis not agreed upon:These problems should clear up as more early Homo fossils are foundPresently, early Homo is foundONLY in Africa (eastern and southern)Most early Homo fossils are veryfragmentary and scatteredWhat sets Homo apart from Australopithecus?The major difference is the first significant increase inBRAIN SIZE(SmithsonianInstitution)A. afarensisHomo habilisFor 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 280-350Modern chimp 285-500 (x=390)There was some slight increase in brain sizeamong australopithecines – not as big as thejump in brain size we get with first HomoHomo habilisFound 2.5-1.6 mya, at end of the Pliocene, intoPleistocene in both east Africa and south AfricaFace smaller, less prognathous. Hint of occipital torus.First significant increase of brain size.VocabularyOccipital torus: a ridge across the occipital boneat the back of the skull (muscle attachment area)Compared to Australopithecus:1. Larger cranial capacity (beginning of trend)2. Less postorbital constriction3. More rounded cranium, no sagittal crest4. Zygomatic arch smaller, less massive jaw5. Smaller, slightly less prognathic face6. Parabolic dental arch (Australopithcus had U-shaped arch)Cranial characteristics:Back teeth still large compared to us, but smaller thanearlier hominids: the beginning of a general trend inhumans toward smaller teethHomo habilis cranial characteristics A. afarensis(Stanford et al. 2006:354)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 alsohad this, but Paranthropus had only one major drain.This is called the Radiator Theory about why brainsize could initially begin to expand very slightly amongAustralopithecines.Larger brain size relative to body size.Endocast: cast of the inside of the skullPostcranial characteristics:Basically the same as australopithecines, excepthands and feet are more modernLike A. africanus, long arms and short legs:Still climbing trees as well as walkingRate of maturation faster than us today, more like apesStill 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 rudolfensisfrom east Africa, around what is now called Lake TurkanaH. habilis was about 4.5 ft tallH. rudolfensis was 5 ft tallWe will consider them all to be H. habilisHomo rudolfensis (H. habilis to us)Large brain (752 ml), less pronounced brow ridge,and less prognathism. Long face but also large molarsFound in east Africa around 1.9 myaSo far only one skull. Elsewhere, several thighbonesmay be H. rudolfensis. Thighbones indicate size of5 ft tall and 144 lbs(Smithsonian Institution)Homo habilisIn other words, we still have relatively few fossilsof Homo habilisDisagreement over how variable H. habilis isIn this class we will lump the variability togetherinto just one early Homo species, H. habilisWhen did language develop and what
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