Chapter 11 Early Hominins Derived human traits small canine and big molars 1 bipedalism 2 Parabolic dental arcade oval shaped rather than really U shaped thick enamel 3 Much Larger brains early hominids didn t have that big of brains 4 Longer juvenile period and increase in life expectancy 5 Elaborate culture Differentiates humans from chimps and apes Genetic data indicate we diverged from chimps 7 5 mya LCA Sahelanthropus tchadensis Toumai in Chad 2002 Now dry late Miocene woodland Animals linked to E Africa 7 6 mya Flat face brow ridge like 2mya Foramen magnum underneath biped 320 350cc primitive teeth Earliest potential hominid Orrorin tugenensis 6 mya 2001 12 fossils partial thigh arm finger mandibles teeth Tugen hills Kenya Molars smaller than ramidus but thick enamel like us suggest hominid arms fingers adapted for climbing thigh bone more human like bipedal Colobus impala fossils so mixed woodland savanna Hominins Diversify 4mya 3 genera 1 Australopithecus anamensis afarensis Kenyanthropus platyops africanus garhi habilis and rudolfensis Homo sediba 2 Paranthropus aethiopicus robustus boisei Anamensis Environment of earliest hominids woodlands More U shaped mandible chin more receding than afarensis and later australopithecines Afarensis Lucy plus 13 other individuals Fauna imply woodland to drier savanna Hadar 4 3mya woodland scrub grassland Laetoli grassland sparsely dotted with trees Primitive ancestral traits cranial capacity is 404cc same as chimp base is flared widest part of skull is at bottom and pneumatized air pockets sub nasal prognathism jaw joint shallow somewhat chimp like compared to later hominids between chimps and humans in U shape Derived traits teeth jaws intermediated between apes humans lucy has thick enamel and not AS U shaped canine dimorphism than chimp but than us Lower p1 has small inner cusp chimp 1 and we have 2 equal sized Although bipedal maybe bent legged gait But pelvis wider may have minimized vertical motion the way our longer legs Ilium oriented more toward back so abductors less efficient Legs shorter in relation to body size so less efficient and slower do Pelvis is much more derived than teeth pelvis came first more bowl shaped Laetoli 3 5 mya best example for australopithecus afarensis Tuttle compared to Machigenga no difference Sexual Dimorphism If sexual dimorphism then like orangutans and gorillas much humans chimps bonobos 1 2 pair bonded with concealed ovulation If 2 different species larger in drier smaller in more forested and more arboreal Ethiopia fossils show range in one site within narrow time span and large femur like Lucy s small one supporting sexual dimorphism Arboreal Since chimps make night nests like most primates perhaps afarensis slept in trees Sussman argues feet hands wrists and shoulder show signs of partial arboreality Fingers and toes are slender and curved for grasping like apes not humans and shoulder able to support body while hanging Locomotion Living in a woodland savannah environment Mixture of arboreal and terrestrial With more efficient bipedalism and less efficient climbing Sleeping in trees protection against predators Gathering food in trees still small bodied Forests started changing from woodland to savannah and drying out Australopithecus africanus Small brain Dart said intermediated between apes humans 1st S Africa 1924 now several sites Dart Location of foramen magnum suggested bipedal Most dismissed thought large brain before bipedalism Taung First Australopithecine discovered Sexual dimorphism Canine dimorphism males 4 6 90 lbs Females 3 9 66 lbs 1 2 1 ht 1 36 1 wt Teeth more modern than afarensis 442cc within sampling range of afarensis Postcrania like afarensis bipedalism seen in pelvis and hip of later finds in S Africa Makapanganst Sterkfontein Dart correct foram mag diagnostic Matured rapidly like chimps not slowly like us Taung assumed 6 yrs because molars erupting our molars erupt at 6 yrs Dean counted daily layers of enamel to see how long it took to reach certain stage and concluded faster growth than chimps Taung only 3 yrs First south African species Kenyanthropus platyops Possibly distorted afarensis Australopithecus garhi Awash Ethiopia 450 cc slightly larger than chimp Very prognathic face Canines premolars and molars larger than afarensis and africanus Sagittal crest Differed from other australopiths but lacked derived features of other hominins Australopithecus aethiopicus L Turkana Kenya black skull KNM WT 17000 Jaw joint similar to afarensis chimps gorillas whereas we have modified hinge Very dimorphic similar postcranially to Australopithecines with small brains relative to body however Also quite different Molars are huge lower jaw large for powerful chewing Sagittal crest for attachment of temporalis muscle Flared zygomatic arch to accommodate chewing muscles making face appear flat Temporalis and masseter muscles are large for heavy chewing Australopithecus boisei Most robust Body somewhat larger molars larger really heavy chewing short body with huge face Australopithecus robustus South Africa Bipedal more heavy chewing than africanus for seeds and nuts and meat Australopithecus sediba Lee Berger 2010 South Africa 2 skeletons 1 9 1 78 mya Closest morphological comparisons are to A africanus and H erectus defined through a unique combination of ancestral and derived traits Cramium Body size and proportion australopith 420 cc Brain Reduced size of the molars and pelvis homo trait smaller molars and less flared pelvis more efficient like next group What does this do to the hominin tree Sediba bypasses all other species to erectus that sediba is the ancestor to all genus homo Australopithecine General Characteristics All species considered hominids Human Appear 4 MYA in Africa All Bipedal One species unknown is ancestral to Homo genus Multiple species lived together chronologically and geographically relying on Small brains chimp sized brains Large jaws post canine megadontia big back teeth Small body size with longer arms and shorter legs non modern First stone tool maker different food resources The Robust Australopithecines Characteristics or Paranthropus Genus General Hard object feeding that required a lot of chewing Sagittal crest Large cheek teeth Flared zygomatic arch Dished face Extreme postorbital constriction Woodland and open woodland habitat becoming savannah habitat Chapter 12 The Genus Homo and Stone Tools Defining genus Homo Larger more rounded brain