hominins

Who were the earliest hominins? HOMININ ORIGINS What differentiates our hominin ancestors?  Large brain size (encephalization)- modern humans have largest cranial capacity (brain size vs body size)  Dentition (as we move through we see a dropping of premolars)  Tool making behavior – standardized is unique characteristic of the genus homo (characteristic tool for every species. TOOL MAKING IS NOT A UNIQUE CHARACTERISTIC OF HOMO)  Habitual BIPEDAL LOCOMOTION  Key features would be found in this missing link e.g . Eoanthropus Dawsoni (Piltdown Man) thought he found the missing link. Not encephalization but habitual bipedalism 9 Human Bipedalism (hallmark trait is habitual bipedalism) 1. Forward foramen magnum 2. Spine ( S shaped spine for humans as center of gravity is wrapped around and C shaped for apes as center of Gravity is low) 3. Basin pelvis ( Ileac hips and Valgus angle so inner angulation of the femur so knee joint is over center of gravity) 4. Long lower limbs 5. Valgus position (station 4 of Tutorial) 6. Foot changes ( toes are last to leave ground and we also have shock absorbers) 7. Ileac blade is wider and shorter and oriented sideways but Apes longer and narrower also oriented to front and back and is ischium is elongated and in humans and hominins its pulled up/shortened Advantages of Bipedalism  See farther (see pray and predators)  travel long distances  Freed the hands (carry and throw things) Disadvantages of Bipedalism  More visible to predators (easily seen by predators)  Expose underbelly (exposing vital organs to predators)  Limits ability to change direction  Reduces speed  Lower backaches  Leg & foot injury Who were the earliest hominins?

1 . Sahelanthropus tchadensis, Chad 7-6 mya  Skull  Unique features not seen on miocene apes  Miocene turning into Plyocene  Forward shifted foramen magnum (habitual bipedalism) 2. Ardepithecus, Aramis, Ethiopia 4.4 mya (reassigned to 5.8-5.2 mya)  Dentition reminiscent of Chimps  Hominin features  Forward foramen magnum  Bipedal? 3. Orrorin tugenesis, 6-mya *bipedal? Kenya All post cranial evidence (valgus angle is the contender for bipedalism) AUSTRALOPITHECINES (first defended hominins, indicative of Pliocene’s) Ape-like from waist up  longer arms relative to legs;  curved flexible fingers and toes o still tree climbing  forward thrust of the face, o large flaring cheek bones-ape like human like from the waist down bipedal: S spine; forward foramen magnum; basin shaped pelvis Australopithecines (Geography and form – who found it, major characteristics including cranial capacity, when did it live) GRACILE FORMS East Africa 1. A . anamensis 2. A. afarensis South Africa 3. A. africanus ROBUST FORMS (paranthropus) East Africa 1. A. boisei 2. A. aethiopicus South Africa

Ape-like cranium:  strong facial prognathism (long snout)  small cranial capacity (aver 420cc) 310-500 cc Ape-like teeth  relatively large incisors  relatively large canines (Compared to modern humans)  ape like shaped dental arcade (parallel rows) AUSTRALOPITHECUS AFRICANUS Original Find : RAYMOND DART (1924) Taung, South Africa 1. TAUNG CHILD (Grassile)  estimated to be 3–4 years of age at death (development more similar to apes/chimpanzees than humans)  brain 405cc (forward shift of foramen magnum) Specific Characteristics of A. africanus (in comparison to A. afarensis ): Dentition:  small incisors and canines  rounded dental arcade Cranium  larger cranial capacity than A. afarensis  more globular cranium Robust Australopithecines (Paranthropus) Limbs/Locomotion  bipedal  Thick bones - prominent muscle markings Cranial Anatomy  sagittal crest  broad vertical face  massive brow ridge  prominent midface and large flaring jaw bone because or masiter  neucal crest Diet and Dentition  large palate and premolars (really large needed to grind food)  massive flat molars, with crowding of the front teeth  deep jaws  herbivore  what makes it robust? Specialization of a fibrous plant diet (masticated before digested) AUSTRALOPITHECUS AETHIOPICUS THE BLACK SKULL ; WT 17000 LAKE TURKANA, KENYA, EAST AFRICA (1985) 2.5 mya Hyper robust  broad face

 massive projection of the upper face  very large palate  large area back teeth primitive traits  Cranial Capacity 410 cc  compound crest  prognathic (long snout )  round dental arcade AUSTRALOPITHECUS BOISEI First Find:  OLDUVAI GORGE (1959)  Mary Leakey  Originally called  “ZINJANTHROPUS BOISEI” by Louis Leakey  1.75 MYA Characteristics of A. boisei  lg body size (34 – 49 kg)  bones thick and robust Cranial Anatomy/ Brain  heavy and massive skull  cheek bones flare out to the sides  Sagittal & nuchal crest  prominent brow ridges  postorbital constriction (behind the eyes)  cranial capacity 500 – 530 cc Diet & Dentition  massive palate & premolars  large flat premolars and molars AUSTRALOPITHCUS ROBUSTUS SOUTH AFRICA First Find: Kromdraai & Swartkrans BROOM & ROBINSON 1948 Dating is not definite: thought to be anywhere from 1.8 – 1 mya Characteristics of A. robustus limbs and locomotion  body size similar to A. africanus (32-40 kg)  thick bones & prominent ms markings  bipedal Cranial Anatomy / Brain  flattened “dished out” face  face positioned high with a low forehead

 Curved fingers Homo traits  Short fingers  Neural reorganization of brain (?)