Pliocene hominins Flashcards

Question

Give cranial details of A. garhi (10)

Answer 1

~450cc lower face is prognathic with procumbent incisors  The zygomatic roots originate above P4/M1 Canine roots are placed well lateral to the nasal aperture margin  The palate is vertically thin The dental arcade is U‐shaped, with slightly divergent dental rows  The temporal lines encroach deeply on the frontal, past the mid‐supraorbital position and likely met anterior to bregma  There is marked postorbital constriction  The parietal bones have a well‐formed, bipartite, anteriorly positioned sagittal crest that divides above lambda  Dentition characterised by relatively large canines, similar to A. afarensis, and large molars

Answer 2

Temporal lines, sagittal crest, and post-orbital constriction suggesting powerful mastication second molar similar to P boisei

Answer 3

elongated skull with small braincase prognathic face shoulders adapted for climbing long arms and hands with curved fingers

Answer 4

central FM (spine connection beneath the skull) robust and broad/ basin-like pelvis to support upper body and keep it upright Valgus angle arched feet

Answer 5

broader than any other early hominin

Answer 6

ape like brachial index (humerus similar size to forearm) | extended femur as in humans

Answer 7

``` Stone tools, and animal bones with cut‐marks were found in nearby strata of same geological context, although not in direct association with the fossil remains. ``` Evidence of butchery – blunt and sharp instruments used – no tools found with garhi fossils but stone tools found a few miles away at Gona

Answer 8

similar dentition to Paranthropus | use of stone tools (similar to Homo)

Answer 9

Found in Chad 2.5 thousand km from Rift Valley - shows Australopithecines were successful enough to range from Ethiopia to South Africa to Chad

Answer 10

1. Significantly more vertical lingual aspect of the mandibular symphysis. 2. Three roots in both third and fourth premolar. ( BUT third premolar of the A. afarensis LH-24 specimen from Middle Awash, Ethiopia, was described by White (2000) as having the same feature, which shows that premolar anatomy was highly variable for A. afarensis)

Answer 11

* size and proportions * Bicuspid P3s * Incisiform canines

Answer 12

afarensis hard to tell without more fossils but if part of afarensis then it is at least a separate population due to great distance between

Answer 13

``` Kenyanthropus platyops From the lower Lomekwi and Kataboi Members of the Nachukui Formation, West Turkana, Kenya 3.5‐3.2 Ma ```

Answer 14

UNIQUE COMBINATION OF PRIMITIVE AND DERIVED TRAITS | NOT OBSERVED IN ANY OTHER HOMININ

Answer 15

``` Flat face, with anterior origin of zygomatic Flat brows Small brain Thick enamel (dental anomaly) Chimp‐like auditory meatus ``` stone tools also found in same location from 3.3mya

Answer 16

Similar homo rudolfensis (1 million years later) – represents early member of parallel lineage leading to homo???? Cannot be tested until more platyops found

Answer 17

• Disagreements as to whether the material assigned to this species is sufficiently different from Au. africanus to warrant being a different species • Disagreements as to what material should be assigned to it 3.67mya - ?

Answer 18

Australopithecus africanus 2.8 ‐ 2.0 Ma • Disagreements as to whether the material assigned to this species should be split into 2 or more groups, including Au. Prometheus, and if so how to group the fossils • Disagreements as to whether the diversity seen reflects sexual dimorphism, and even as to which fossils are likely to be male or female • Disagreements about whether individual fossils show affinities to P. robustus or Homo

Answer 19

3 – africanus, Prometheus, sediba

Answer 20

Australopithecus sediba 2.0 Ma • Disagreements about the phylogenetic, evolutionary and adaptive interpretation of the morphology of the fossils

Answer 21

Ravaged by carnivores – carried to sites by birds of prey 2. Fossils within solid breccias, compressed by weight of sediments, rocks, etc – makes extraction hard 3. Complex stratigraphy of the caves – deposites form in non-linear manner 4. Caves mined by explosions for limestone 5. Exploded fossiliferous cave sediments mixed by mining explosions – even harder stratigraphy 6. Ravaged by scholarly argument over 95 years – are austra a single genus

Answer 22

1. Ontogeny (Many austro skeletons in these caves are children – remember different parts of the body grow at different rates ) 2. Sexual dimorphism 3. Intraspecific temporal trends Interspecific diversity

Answer 23

often decided by cranial features, easier in apes than humans, who vary by degree rather than kind

Answer 24

eg difference in jaw from different diet but not rest of skull; as individuals become part of a different evolutionary lineage the different features will accumulate – when does it become taxonomic differences – different scientists have different focuses

Answer 25

Found in Sterkfontein and Makapansgat MLD2 Prometheus abandoned in the 50s, but based on similarities on a recent discovery (StW573) from Sterkfontein with those from Makapansgat, suggested Prometheus should be revived – disputed ages – long lived and contemporaneous with africanus ‘Little foot’

Answer 26

• Estimated brain size: ≥ 408 cc • Sagittal and nuchal crests; pronounced ridge for nuchal ligament • Large face, prognathic • Tall midface • Rounded supraorbital tori • Strong maxillary pillars, contiguous with canine root • Hollowed pre‐nasal fossa (neither sloping or sharp edge) • Large, deep mandible, with vertical inferoposterior aspect

Answer 27

Large anterior dentition, particularly upper I1s • Three‐rooted premolars • Extreme dental wear on I1‐M1, little on M2s, virtually none on M3s • Diastema between upper lateral incisors and canines importantly the anterior dentition (esp canines) are different from africanus

Answer 28

Absolutely larger than A.L. 288 (Lucy, Au. afarensis), but similar body proportions • Apically narrow thorax • Cranially oriented glenoid fossa of scapula • Little humeral torsion, similar to A.L. 288 and Sts 7 • Climbing adaptations in humerus and ulna; radius curved like Au. garhi • Habitual (terrestrial bipedalism • Ape‐like features of the tibia

Answer 29

wide, flaring supracondylar ridge and large epicondyle – well developed brachioradialis and wrist/ digital extensor muscles shape of pelvis, muscle insertions of medial malleolus

Answer 30

Similar brachial index to Lucy

Answer 31

Habitual biped | Leg foot articulation less efficient than afarensis – lag changes of upper limb, adaptive retention of arboreal traits

Answer 32

Height: 1.1 to 1.4 m Weight: 30 to 60 kg

Answer 33

Loss of curved phalanges of afarensis

Answer 34

cranial capacity: 400‐500 cm3 rounded vault variable cranial crest Moderate facial prognathism (more so than prometheus) Moderately large jaws and teeth Trend towards megadonty and reinforcement of mandible FM well belox vault – vertical connection to spine

Answer 35

• Most postcranial fossils are isolated elements or parts of elements • There may be some functional differences within the sample in the proximal tibia, hallucial and 2nd metatarsals, and a clavicle from the older Jacovec cavern at Sterkfontein • Bipedal adaptations in the distal tibia and human‐like gait

Answer 36

Trabecular bone indicates human like gait | Human like distribution of trabecular bone in hand – used for holding and grabbing – NOT walking

Answer 37

yes: Weight 30-40kg

Answer 38

Makapansgat, 3.0‐2.8 Myr Sterkfontein, Member 4, 2.8‐2.0 Myr Gladysvale, ~2.5 Myr Taung, ~ 2.3 Myr ```  Makapansgat, South Africa  Member 2, Sterkfontein, South Africa (3.67 ± 0.16 Ma)  Member 4, Sterkfontein, South Africa  StW 573 skeleton [“Little foot”] from the Silberberg Grotto at Sterkfontein ( ```

Answer 39

in 2008, at the cave of Malapa, South Africa new species named in 2010 Dated to ~1.95 – 1.977 Ma

Answer 40

hyper‐pronating gait

Answer 41

``` MH1 (juvenile): australopithecine cranio‐facial shape and size ‐ 420 cc brain narrow face, different from other australopithecines ```

Answer 42

MH1 and isolated mandibular and maxillary fragments: enlarged molars typical of Australopithecus, but not megadontic – small tooth size, similar to the tooth size of our genus Homo affinities to Au. africanus in non‐metric dental traits, but not East African forms – South African clade

Answer 43

Similar brain size as chimpanzees  larger frontal lobe  Larger area in the inferior frontal gyrus  In humans, the inferior frontal gyrus is associated with language and social behaviour

Answer 44

•Long arms, climbing adaptations •Ape ‘shrugged’ shoulders •Apically narrow thorax •Vertebrae suggest a functionally longer and more flexible lower back than in humans •Spine curvature more derived than in australopithecines

Answer 45

Short fingers that are curved strong flexor apparatus elongated thumb – precision grip? much longer than pan

Answer 46

``` pelvis ‐ incomplete in both skeletons, so reconstructed as a mosaic of the parts preserved in both Some features shared with Au. Africanus: • Bi‐acetabular width, small sacral and coxal joints Some features shared with Homo: • Robusticity of iliac body, sinusoidal anterior iliac borders, shortened ischia, and superiorly oriented pubic rami Very small birth canal Small acetabulum ```

Answer 47

Leg‐ankle articulation: tibia vertically above foot, as in bipedal hominins Ape‐like gracile calcaneal body, robust medial malleolus Homoplasy in the bipedal adaptations in the hominin foot, and a different mode of bipedalism Interpreted as having walked with fully extended leg and an inverted foot during the swing phase

Answer 48

Human like arch suggests human like ligaments and Achilles tendons but weight was on small angled surface rather than broad heel – different form of bipedalism Walked with fully extended leg and inverted foot

Answer 49

Australopithecus prometheus 3.67 ‐ ? Ma • strongly based on StW 573 older skeleton • inclusion of younger fossils from Member 4 at Sterkfontein controversial Australopithecus africanus 2.8 ‐ 2.0 Ma • Heterogeneous set of fossils • Division into two morphs not clear • Some indication of more human‐like body than observed in the StW 573 skeleton Australopithecus sediba 2.0 Ma • Unique hominin, with a small brain, but also small teeth • Ape‐like upper body, but with different hands – short fingers, but curved, and long thumbs • Different form of bipedalism from any other hominin

Answer 50

Berger suggested sediba’s stance is the best candidate for what lead to homo – v controversial