Paleoanthropology The study of human origins and evolution, focuses on the tiny fraction of geologic time during which humans and chimpanzees diverged from a common ancestor. Some Common Misconceptions • Human ancestors were chimpanzees – Chimpanzees and humans represent two divergent branches of the hominoid tree that evolved from a common ancestor that was neither a chimpanzee nor a human. Some Common Misconceptions • Human evolution is like a ladder with a series of steps leading directly from an ancestral hominoid to Homo sapiens. •At times in hominid history, several different human species coexisted. •Human phylogeny is more like a multibranched bush than a ladder, our species being the tip of the only twig that still lives. 0 Paranthropus Homo ? robustus ergaster 0.5 Paranthropus boisei 1.0 Homo 1.5 Australopithecus sapiens africanus Homo 2.0 Australopithecus neanderthalensis afarensis 2.5 Homo 3.0 Australopithecus erectus anamensis 3.5 Homo habilis 4.0 Kenyanthropus platyops 4.5 Ardipithecus 5.0 ramidus 5.5 6.0 Orrorin tugenensis 6.5 Sahelanthropus tchadensis 7.0 D.3.6: State that, at various stages in hominid evolution, several species may have coexisted. Hominid Evolution: the current view A modern view of human evolution maintains that it has occurred as a series of adaptive Megadonts radiations. African apes Early Bipedal Apes Time (millions (millions of years) Time Diversity Hominid Evolution: the current view The 1st radiation: is that of the early bipedal apes – including the gracile Australopithecines. Megadonts African apes Early Bipedal Apes Time (millions (millions of years) Time Diversity Hominid Evolution: the current view The 2nd radiation: involved the robust Australopithecines, a group of species that exploited low-grade vegetable food Megadonts sources (nuts, root tubers and seeds) African apes resulting in species Early Bipedal with very large teeth Apes (megadont). (millions of years) Time Diversity Hominid Evolution: the current view 3rd radiation: is genus Homo, developing a larger brain, diversifying, and Megadonts dispersing from Africa to other African apes Early parts of the Old Bipedal Apes World. (millions of years) Time Diversity Hominid Evolution: the current view 4th radiation: does not involve any major evolutionary Megadonts divergence, but reflects the African apes dispersal of Early Bipedal modern humans Apes worldwide. (millions of years) Time Diversity Genus Homo Neanderthals became extinct Modern humans Hominid about 35,000 arose 150,000 to Holocene years ago 100,000 years ago 0 Homo Homo sapiens Evolution neanderthalensis 0.5 Many human Robust Australopithecines 'prototypes' exist regionally Archaic A greatly Homo sapiens 1 simplified Pleistocene Split by some into depiction of Homo erectus and Homo ergaster Homo erectus Paranthropus hominid Paranthropus robustus 2 boisei Split by some into evolution. Homo habilis and Homo rudolfensis Homo habilis (1470 skull) Paranthropus aethiopicus Uncertainty as to whether present Million beforeyears Australopithecus A. africanus was a direct 3 ? africanus human ancestor A. afarensis ('Lucy') is the earliest currently known human ancestor Pliocene Australopithecus A second sub-species afarensis (A.r. kadabba) 5.2-5.8 mya Possible hominid 4 near hominid/ape split at 6.0 mya ? Genus Homo ? ? Australopithecus Genus Australopithecus anamensis Orrorin Genus Paranthropus Ardipithecus tugenensis ramidus ramidus 6.0 mya 5 The Hominid Fossils *We will only discuss a small selection of hominid fossils. There are others that time does not allow us to include. There are 7 species of hominid for which we need to be familiar… Ardipithicus ramidus Date 4.4-5.8 mya Brain Size 300-350 cc Height c. 1.22 m Physique Possibly bipedal forest dweller. Little else known. Skull shape Foramen magnum more forward than apes Teeth and Teeth intermediate jaws between earlier apes and later hominids. Reduced canine teeth. Smaller, narrow molars; thinner jaw. Distribution Eastern Africa Reading: Oldest Skeleton of Human Ancestor Found Reading: Meet the new human family (Ardi section…) Australopithecines are divided into two groups Learn about us first! A. africanus A. boisei Gracile, small boned ape-like forms Robust, ape-like forms (A. africanus, A. afarensis) (A. boisei, A. robustus) RADIATION #1 RADIATION #2 Australopithecus afarensis Date 3.9-2.5 mya Brain Size 400-500 cc Height 1.07 – 1.52 m Physique Light build. Bipedal. Some apelike features: relatively long arms, curved fingers, sexual dimorphism* Skull shape Apelike face, low forehead, bony brow ridge, flat nose, no chin Teeth and Canines smaller than apes, jaws larger than humans. Jaw shape half way between an ape and human * Some researchers claim such differences in height suggest two separate species, not sexual Distribution Eastern Africa dimorphism. Jaw shape half way Sexual dimorphism between V-shape of in the canine teeth ape's and U-shape (a primitive trait) of human jaw Shoulder joint that is orientated Chest (thorax) towards the head is funnel- shaped Relatively long arms compared to legs Wrist has high mobility Finger bones Relatively are curved short legs Ankle joint is Toes are long highly mobile and curved Redrawn from a photograph by © David L. Brill 1985 Australopithecus afarensis Small brain (410cc) Low forehead Brow ridge Large, dish- shaped face Wide midface Flat nose Big, ape-like Little of the skull is incisor behind the foramen Diastema magnum (gap) Large, thickly Canines larger enameled molars than in humans A Modern Human Skull (for comparison) Australopithecus africanus Date 3.0-2.3 mya Brain Size 400-500 cc Height 1.1 – 1.4 m Physique Light build. Probably long arms, more „human‟ features, probably less sexual dimorphism than A. afarensis Skull shape Brow ridges less prominent; higher forehead and shorter face. Teeth and Teeth and jaws much jaws larger than in humans; shape of jaw fully parabolic as in humans; canine teeth further reduced Distribution Southern Africa Australopithecus africanus Small brain (450cc) same size as gorilla's but organization is No sagittal crest different from an ape's Brow ridge Low facial angle Lower face protrudes forward into a snout Very large molars compared with (prognathism) modern humans (not shown here) A Modern Human Skull (for comparison) Australopithecines are divided into two groups Now learn about us (even if IB doesn‟t care about us!) A. africanus A. boisei Gracile, small boned ape-like forms Robust, ape-like forms (A. africanus, A. afarensis) (A. boisei, A. robustus) RADIATION #1 RADIATION #2 A. robustus A. boisei A. aethiopicus Australopithecus robustus (AKA Paranthropus) Date 2.2 – 1.5 mya Brain Size 530 cc Height 1.1 – 1.3 m Physique Heavy build. Relatively long arms. Moderate sexual dimorphism. Skull shape Long, broad, flat face. Crest on top of skull. Moderate facial buttressing. Teeth and jaws Thick jaw, small incisors and canines. Large molars. Distribution Southern Africa A. robustus Very prominent sagittal crest for the attachment of powerful jaw muscles Small brain (530cc) Heavy brow ridge Part of the rear and top of this skull is missing Low facial angle Massive zygomatic arch and cheek bones Little of the skull is behind the foramen magnum Small incisors (missing in this specimen) Massive molars with thick enamel are well worn suggesting a tough A Modern Human Skull vegetarian diet (for comparison) Genus Homo Homo habilis Homo neanderthalensis Homo ergaster Homo erectus Archaic Homo sapiens Homo sapiens Homo habilis Date 2 – 1.6 mya Brain Size 500-800 cc Height 1.0 – 1.5 m Physique Robust but “human” skeleton Skull shape Small face with developed nose Teeth and Narrow molars. jaws Distribution Eastern and Southern Africa Homo habilis Bigger brain Rounded cranium with no sagittal crest (650-680cc) Bulge in the Broca's area Brow ridge of the brain for speech production Smaller, narrower face than the australopithecines Flat nose Projecting jaw More of the skull is behind (prognathism) the foramen magnum Tooth row displays a Jaw is less massive than modern curve, with in the australopithecines narrow molars A Modern Human Skull (for comparison) Homo erectus Date 1.8 – 0.3 mya Brain Size 750 - 1250 cc Height 1.3 – 1.5 m Physique Robust but “human” skeleton Skull shape Flat, thick skull with sagittal “keel” and large brow ridge Teeth and Smaller teeth than H. jaws habilis Distribution Africa, Asia, Indonesia and possibly Europe Homo erectus Bulge in the Broca's Bigger brain Long, flattened cranium with a area of the brain for Earliest: 750cc distinctive keel along the top speech production Latest: 1250cc Bulge in Wernicke's Shelving area of the brain for forehead speech recognition Thick brow ridge Flat face Occipital lobe Projecting (bun-like swelling) jaw Attachment for strong neck muscles to stop the head from sagging forward Teeth are smaller than A Modern Human Skull H. habilis, but more No chin (for comparison) massive than our own In Europe, H. erectus gave rise to the Neanderthals Homo neanderthalensis Date 150,000 – 30,000 ya Brain Size 1250 – 1750 cc Height 1.5 – 1.7 m Physique Robust but “human” skeleton, adapted for cold. Skull shape Reduced brow ridge, midface projection, long low skull Teeth and Similar to H. sapiens, jaws larger jaw Distribution Europe and western Asia Key 30,000 years ago Atlantic Ocean 30,000–35,000 years ago 35,000 years ago Original discovery Approximate range of Neanderthals Europe Neander Valley Black Sea Mediterranean Sea Africa Homo neanderthalensis Large brain (1600cc) Low, long cranium Larger