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Question 1

Sahelanthropus tchadensis [6-7 mya]

Answer 1

Less prognathic face than would be expected for an early hominin. Anteriorly placed foramen magnum. However, has a small brain size and a U-shaped dental arcade.

Question 2

Orrorin tugensis [6 mya]

Answer 2

Inconclusive evidence of bipedality in the femur and the arm. Larger body size than expected for a late Miocene. Small teeth with thick enamel, but a canine that is more apelike.

Question 3

Ardipithecus kadabba [5.8-5.2 mya]

Answer 3

More apelike dentition than Ardipithecus ramidus.

Question 4

Ardipithecus ramidus [4.4-3.9 mya

Answer 4

Slight change in locomotion. Had an opposable thumb, flexible hands, a long and flexible lower back. Retained primitive lower pelvis and thigh. Low sexual dimorphism. Small brain [300-350 cc].

Question 5

Australopithecus anamensis [4.2-3.9 mya]

Answer 5

Firm evidence of bipedality in the tibia. Dentition that is more derived than Ardipithecus but more primitive than later hominids. U-shaped dental arcade, with thicker molar enamel.

Question 6

Australopithecine Trends

Answer 6

High sexual dimorphism indicates that they were not solitary. Trend towards bipedalism: some say it was habitual, but others contend that they used a mixed arboreal/bipedal tactics. Angled femurs broken by a larger medial condyle. and broader/shorter pelvises. An arched foot, with a large anklebone. Relative decrease in incisor and canine size; decrease of premolar and molar sizes. Loss of CP3 complex, with U-shaped dental arcade. Brain size of 400-550 cc. Funnel-shaped ribcage, longer arms than legs, and curved fingers and toes.

Question 7

Australopithecus afarensis [4-3 mya]

Answer 7

Cranial capacity of 400-500 cc. Skull was very prognathic, with relatively large incisors and canines. An intermediate dental arcade still close to a U-shape. Temporal muscles were set well back on the cranium; sagittal crest. Clear indications of bipedalism in the bones and the non-divergent big toe, but curved fingers and toes. Likely that they were living in groups and not monogamous because they were very sexually dimorphic.

Question 8

Australopithecus bahrelghazalia [3.5-3.2 mya]

Answer 8

Research suggests that dentition is different from afarensis.

Question 9

Kenyanthropus platyops [3.5-3 mya]

Answer 9

A surprisingly flat face, which is a derived trait of later hominins. However, molars are smaller, and thus more primitive, than the australopithecines.

Question 10

Australopithecus africanus [3-2 mya]

Answer 10

Cranial capacity of 400-500 cc. Less prognathic than A. afarensis. Small incisor-like canines with no C/P3 complex. Larger premolars and molars. Brow ridges less prominent than afarensis; no cranial crests. Bipedal, with relatively longer arms and shorter legs

Question 11

Australopithecus garhi [2.5 mya]

Answer 11

Small brain [450 cc], a prominent prognathic face, large canines, a sagittal crest. Primitive and similar to afarensis, save for the fact that it has larger cheek teeth and a slightly larger canine. May have more human qualities in its legs (femur is long for striding) but more apelike qualities in its arms.

Question 12

Robust Australopithecine/Paranthropine Trends

Answer 12

The robust australopithecines appear to have lead to a dead end because of their extreme adaptions to hard object feeding. Their molars have extreme force to crack open nuts, but when the landscape changed, their fallback food did too. Several adaptions to this eating pattern include a sagittal crest, flared zygomatic arches, and huge molars. Some scientists think that the robust australopithecines are so different from other australopithecines that they should be put in a genus of their own.

Question 13

Australopithecus/Paranthropus aethiopicus [2.8-2.2 mya]

Answer 13

Cranial capacity of 410. Large sagittal crest with a compound crest. Broad and prognathic face with dish-shaped midface. Facial buttressing and unflexed cranial base like A. afarensis. Position of foramen magnum indicates bipedalism. Huge molars and large anterior teeth.

Question 14

Australopithecus/Paranthropus boisei [2.3-1.2 mya]

Answer 14

Cranial capacity of 500-530 cc. Prominent sagittal and nuchal crests that are not compound. Broad, flattish face with strong facial buttressing, a dish-shaped midface, and a very thick jaw. Small incisors and canines with very big premolars and molars; thick enamel. Habitual biped with relatively longer arms than legs.

Question 15

Australopithecus/Paranthropus robustus [2-1 mya]

Answer 15

Cranial capacity of 500-550 cc. A sagittal crest is present, but it is not a compound crest. Broad, flattish face with moderate facial buttressing, a very thick jaw, and a dish-shaped midface. Small incisiors and canines with large premolars and molars, but not as large as boisei. Habitual biped with relatively longer arms than legs.

Question 16

Australopithecus sediba [1.98 mya]

Answer 16

Shares derived characteristics with Homo including dental size/shape, a broad frontal, facial shape, and pelvis features.

Question 17

Homo habilis [2.33-1.44 mya]

Answer 17

Brain size increased by 20 percent to 500-800 cc, and reorganized so that the lunate sulcus was in a hominin position. A parabolic arcade, with bigger anterior and smaller posterior teeth. Higher and rounder skull that was not as prognathic. Skull bones were somewhat thinner. Evidence of bipedalism from the foramen magnum, a non-divergent big tow, an arched foot, a large anklebone. However, arms are still longer than legs

Question 18

Homo rudolfensis [2.33-1.44 mya]

Answer 18

Larger brains (600-800 cc) than the smaller form/H. habilis (500-674 cc). Australopithecine-like face compared to Homo habilis. Larger teeth sitting in a thick jaw.

Question 19

Homo erectus [1.8-.2 mya, .1 in SE Asia]

Answer 19

Skull is low front to back, low and flattish with thick bones and a sagittal keel. Has a thick brow and sloping forehead. Shovel sized incisors and reduced molars. The brain is 20-25% larger than that of Homo habilis – 700/750-1250 cc. Petalias indicate handedness. Asian skulls have thicker straighter brows, more sloping foreheads, a sagittal keel, and a stronger occipital angle and torus.

Question 20

Homo ergaster [1.8-.2 mya]

Answer 20

African skulls have thinner or more curved brows, a less sloping forehead, no sagittal keel, and a less strong occipital angle and torus compared with Asian forms.

Question 21

Homo heidelbergensis [.8-.2 mya]

Answer 21

A uniform 11% increase in brain size from Homo erectus and concomitant changes in cranial shape. This hits the range of modern human brain size. Higher and rounder skull compared with Homo erectus, with the maximum skull width higher on the skull. A less prognathic face, with a rounder occipital and reduced torus. Modern human body plan.