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Human Evolution > Pliocene hominins > Flashcards

Pliocene hominins Flashcards

1
Q

What do australopithecines indicate in human evolutionary trajectory

A

Australopithecines indicate turning point of becoming obligate bipeds

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2
Q

Who were the australopithecines in East Africa? (6)

When did they exist?

A 
Australopithecus sp. 5.5 Ma
Australopithecus anamensis 4.2 – 3.8 Ma
E Africa
Australopithecus afarensis 3.9 – 2.9 Ma
Australopithecus deyiremeda 3.4 Ma
Australopithecus garhi 2.5 Ma
Kenyanthropus platyops 3.5 Ma
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3
Q

Which Australopithecine lived in central Africa? When?

Which Australopithecines lived in South Africa?

A

Australopithecus bahrelghazali 3.5 Ma

Australopithecus prometheus 3.67 Ma
Australopithecus africanus 3.3 ‐ 2.1 Ma
Australopithecus sediba 2.0 Ma

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4
Q

Give 3 key features of a genus

A

Monophyletic
Shared ecological niche
Distinctiveness

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5
Q

Give key facts about Australopithecus anamensis (7)

A

4.2 – 3.8 Ma
More derived than Sahelanthropus, Orrorin or Ardipithecus
365‐370 cc, large face, rounded nasal aperture, sagittal crest
Enlarged molars, with parallel mandibular postcanine tooth rows
Thick tooth enamel
Variable body size (assumed to be sexual dimorphism)
Obligate bipedal adaptation

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6
Q

Where are the oldest members of Australopithecus found? And the youngest?

A

Oldest – east Africa – anamensis – also largest number of australopithecines and only location of kenyanthropus

Most recent in South Africa – sediba (2ma)

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7
Q

Where are all the australopithecines from central Africa found

A

Central all found in koro toro in chad

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8
Q

Give 6 key facts about A. afarensis

A 
3.9 – 2.9 Ma
365‐526 cc
Enlarged molars
Thick tooth enamel
Variable body size (considered to be sexual dimorphism)
Obligate bipedal adaptation
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9
Q

What is the type specimen of A. afarensis

How many fossils exist for this species

A

LH 4 mandible, Laetoli
(most material discovered at Hadar)

Presently known from hundreds of fossil specimens

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10
Q

What environments is Australopithecus likely to have lived in?

A

Mixed woodland and grassland evirons – so chimps and gorillas would be found in central and w Africa
Discovery in chad suggests austrolopithecines had a greater range even for a short time – not in north Africa – Pliocene has not be dug up across Africa so don’t know yet

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11
Q

What is necessary to be part of the australopithecine genus

A

originally anything between apes and human; now – obligate biped that share a ecological niche with large molars and thick dental enamel, but are neither megadonte or encephalised – different from homo and paranthrapus

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12
Q

What was found at Lothagam? Why does it matter to Australopithecus evolution?

A

fossils from late Miocene to Pliocene – west turkana – 2 hominin teeth – right lower incisor and wisdom tooth – similar to Australopithecus but from 5-4.2mya

Australopithecus sp.?

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13
Q

What are the bipedal adaptations of anamensis’ tibia

A

angle of articulation, enlarged lateral condyles, prominent interconylar eminence, consistent with locking knees, tibia and talus is horizontal like us (not chimps)

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14
Q

How did male anamensis differ from females

A

females(?) =2/3 size of males

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15
Q

Give poscranial details of afarensis

A

Height: 1.0 – 1.5 m; Weight: 30 to 70 kg
 Short, wide sacrum, with flaring ilia
 Dorsal scapula
 Relatively long arms and curved phalanges in
both hands and feet

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16
Q

Give dental details of afarensis

A 
 Prognathic face, canine fossa
 Dental diastema in some individuals
 relatively large mandibular ascending ramus and 
deep corpus, with receding symphysis
 Anterior dentition relatively large
 Canines smaller than earlier hominins 
 Unicuspid P3
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17
Q

IS A. afarensis sexually dimorphic

A

 Extremely variable and/or very sexually
dimorphic – equivalent to Pongo or Gorilla
 Sexual dimorphism expressed in the post‐crania,
but not in the canines

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18
Q

What is the fossil group , “The First Family”?

A

 A.L. 333 Site [~3.2 Ma],
discovered in 1975 by Donald Johanson’s team at
Hadar, Ethiopia. Remains of at least 13 individuals of
different ages.

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19
Q

Which important afarensis fossil was found at Dikika

Give key features

A

3y/o child

 3.3 Myr
 ~3 yrs old – early onset of typical afarensis features
 a hyoid bone that has a typical African ape morphology
-face is small cf skull, 275cc, grow to nearly 425cc,
 foot and other parts of lower limb show evidence of bipedal locomotion
 gorilla‐like scapula and long and curved manual phalanges ‐ arboreal behaviour

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20
Q

What microevolutionary trend characterizes the evolution of Australopithecus afarensis?

A

Increased size of mandible through time

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21
Q

What is the geography and temporal range of Australopithecus deyimereda

A

 3.5‐3.3 Ma
 Waytaleyta, Burtele (Woranso‐
Mille area, Ethiopia)

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22
Q

How derived are the features of Au. deyiremeda compared to Ar. ramidus

How does deyiremeda compare to anamensis

A

More derived than Ar. ramidus
(thicker enamel, more complex
tooth roots, more robust
mandible)

More robust mandible, and
vertical mandibular symphysis
than Au. anamensis

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23
Q

Why is Australopithecus deyimereda in a new taxon

Why is this species important for understanding the Pliocene era of human evolution

A 
More derived than Ar. ramidus
(thicker enamel, more complex 
tooth roots, more robust 
mandible)
 More robust mandible, and 
vertical mandibular symphysis 
than Au. anamensis
 Different from Au. afarensis, Au. 
garhi, Kenyanthropus, 
Paranthropus and early Homo, 
hence new taxon
some aspects of teeth and jaw are similar to Paranthropines - could be convergence?

shows that Australopithecines had diversified into different species that lived alongside one another

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24
Q

Which australopithecine was named in 1999

When/ where did it exist

A

A. gahri

From the Hata Member of the Bouri
Formation, Middle Awash, Ethiopia, originating
from several sites (Matabaietu, Gamedah, Bouri)
~2.5 Myr

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25
Q

Give cranial details of A. garhi (10)

A

~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

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26
Q

What can be inferred about the masticatory abilities of A. garhi

A

Temporal lines, sagittal crest, and post-orbital constriction suggesting powerful mastication

second molar similar to P boisei

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27
Q

What features do chimps share with Lucy

A

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

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28
Q

What features does Lucy share with humans

A

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

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29
Q

What is interesting about A. garhi’s canines

A

broader than any other early hominin

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30
Q

Describe key post cranial features of A. garhi

A

ape like brachial index (humerus similar size to forearm)

extended femur as in humans

31
Q

Did A. garhi use tools?

A 
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

32
Q

What features of garhi are convergent with other early hominins

A

similar dentition to Paranthropus

use of stone tools (similar to Homo)

33
Q

Why is Australopithecus bahrelghazali exciting

A

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

34
Q

What are the distinguishing features of A. bahrelghazali

A
  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)
35
Q

What features are Au. anamensis and/or Au. afarensis:

A
  • size and proportions
  • Bicuspid P3s
  • Incisiform canines
36
Q

What species could bahrelghazali be subsumed into

A

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

37
Q

Where / when did Kenyanthropus exist

A 
Kenyanthropus platyops
From the lower Lomekwi and 
Kataboi Members of the Nachukui
Formation, West Turkana, Kenya
3.5‐3.2 Ma
38
Q

what is interesting about Kenyanthropus platyops

A

UNIQUE COMBINATION OF PRIMITIVE AND DERIVED TRAITS

NOT OBSERVED IN ANY OTHER HOMININ

39
Q

Kenyanthropus has UNIQUE COMBINATION OF PRIMITIVE AND DERIVED TRAITS
NOT OBSERVED IN ANY OTHER HOMININ. what are they

A 
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

40
Q

Which species is very similar to Kenyanthropus

A

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

41
Q

What is controversial about A. prometheus

When was it said to have existed

A

• 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 - ?

42
Q

What are the disagreements associated with A. africanus

A

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

43
Q

How many southern African members of Australopithecus have there been?

A

3 – africanus, Prometheus, sediba

44
Q

what is controversial about Australopithecus sediba?

A

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

45
Q

Why are the fossils from southern Africa so hotly debated?

A

Ravaged by carnivores – carried to sites by birds of prey

  1. Fossils within solid breccias, compressed by weight of sediments, rocks, etc – makes extraction hard
  2. Complex stratigraphy of the caves – deposites form in non-linear manner
  3. Caves mined by explosions for limestone
  4. Exploded fossiliferous cave sediments mixed by mining explosions – even harder stratigraphy
  5. Ravaged by scholarly argument over 95 years – are austra a single genus
46
Q

What 3 processes give rise to variation within a species

What is another process leading to variation

A
  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

47
Q

How is dimorphism examined in ancient hominins

A

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

48
Q

Demonstrate the importance of interspecific diversity when studying ancient hominins

A

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

49
Q

Why did Clark suggest that the name Australopithecus prometheus should be revived?

A

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’

50
Q

What are the cranial features of Au. Prometheus

A

• 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

51
Q

What is the dentition of A prometheus like (4)

A

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

52
Q

Describe the post crania of A. prometheus

A

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

53
Q

What climbing adaptations did A. prometheus have?

Did it have any bipedal adaptations

A

wide, flaring supracondylar ridge and large epicondyle – well developed brachioradialis and wrist/ digital extensor muscles

shape of pelvis, muscle insertions of medial malleolus

54
Q

How does A. prometheus’ brachial index compare to afarensis?

A

Similar brachial index to Lucy

55
Q

What is the locomotion of A. prometheus

A

Habitual biped

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

56
Q

What was the height and weight of Au. africanus

A

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

57
Q

Compare the phalanges of africanus and afarensis

A

Loss of curved phalanges of afarensis

58
Q

Describe the cranium of africanus (3)

Describe the face of africanus (3)

FM?

A

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

59
Q

Describe the postcrania of africanus (3)

A

• 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

60
Q

What can we learn from the trabecular bone of africanus

A

Trabecular bone indicates human like gait

Human like distribution of trabecular bone in hand – used for holding and grabbing – NOT walking

61
Q

Does africanus show sexual dimorphism?

A

yes: Weight 30-40kg

62
Q

Where has africanus been found?
What dates are associated with these fossils?

Where has prometheus been found supposedly

A

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 (
63
Q

When was Au sediba discovered? Where? How old?

A

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

64
Q

What kind of gait is inferred from sediba’s anatomy

A

hyper‐pronating gait

65
Q

Describe the craniofacial features of sediba

how does it compare to other australopithecines

A 
MH1 (juvenile): 
australopithecine cranio‐facial 
shape and size ‐ 420 cc brain
narrow face, different from 
other australopithecines
66
Q

describe the dentition of sediba

how does it compare to other hominins

A

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

67
Q

How does the brain of sediba compare to other mammals

why is this important

A

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

68
Q

Describe the torso of sediba (5)

A

•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

69
Q

What features do sediba’s upper limbs have

A

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

70
Q

Describe the pelvis of sediba how does it compare with other hominins

A 
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
71
Q

Give the 3 important features of sediba’s foot

how can this be interpreted?

A

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

72
Q

Describe the locomotion of sediba

A

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

73
Q

Describe the key fossil evidence for Au prometheus, africanus and sediba

A

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

74
Q

What did Berger suggest about sediba’s locomotion

A

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

Human Evolution (16 decks)

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