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Human Evolution > Small bodied hominins > Flashcards

Small bodied hominins Flashcards

1
Q

How old is the Homo floresiensis material?

cc?

How tall?

A

From Flores, Indonesia – 60-100kya

417cc,

106cm tall

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2
Q

What are the key features of the Homo floresiensis skull

A 
 Short, orthognatic face
Gracile supraorbital torus
 Thicker cranial vault bones than 
Australopithecus, ~ to Homo
 Small post‐canine dentition
No chin 
 M1 = M2 in size
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3
Q

What is strange about the P3 of Homo floresiensis?

A

very large

Longer AP than basolaterally – unseen before

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4
Q

Size and weight of floresiensis

A

106cm, 30kg

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5
Q
  1. Comment on the robusticity of Homo floresiensis jaw:
A

Very robust for its body size – seen in corpus and symphyseal robustity

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6
Q

What are the derived/ humanlike bipedal traits of H floresiensis

A

• Hallux: adducted

• Arches: plantar
Efficient biped
Primitive traits found throughout skeleton

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7
Q

What are the unique bipedal traits of floresiensis

A

• Proportions of the foot: clusters with chimps

• Foot length to body size: ditto
foot almost as long as lower leg
• Pace: could walk but NOT run (inside of arch, and no spring‐like
mechanism)

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8
Q

Did H floresiensis make tools

A

Made stone tools
• Similar to ~800 Ka tools at Mata Menge site in Flores and possibly 1050 Ka Wolo
Sege site?
• Hunted dwarfed elephants (Stegodon) and giant varanid lizards (Komodo dragon)
• Stegodon: 1st recorded at Wolo Sege

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9
Q

When did H floresiensis go extinct

What happens in Flores after this

A

46kya

youngest H. floresiensis bone remains in the cave date to 60kya, and the youngest stone tools to 50kya, similar time to arrival of modern humans - ‘smoking gun’ (Roberts, 2016) for human-floresiensis competition, but haven’t ‘found the bullet’

giant birds and stegodon probably went extinct at same time

There is a gap in the stratigraphy and then stone tools appear – appearance of modern humans – were they associated with modern humans

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10
Q

What are the different options for what floresiensis is (5)

A
  • Pygmy H. erectus
  • Microcephalic pathological modern human
  • H. habilis
  • Australopithecine
  • None of the above
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11
Q

What is the evidence that Homo floresiensis not a different hominin, but a pathological population

A

stature is within the range of modern humans with Laron Syndrome

short, slightly prognathic also charactersitic of LS and GH deficiency. under-developed chin is also symptom of LS - all seen in floresiensis

LS patients are also known to manifest abnormal body proportion, which is expressed by disproportionately short legs relative to the upper trunk, resulting in an abnormal upper/lower body ratio, as seen in floresiensis

floresiensis has LS due to inbreeding on island of flores?
(Hershkovitz, 2007)

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12
Q

What is Laron Syndrome

A

primary or classical GH insensitiv-ity or resistance)

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13
Q

What derived features does floresiensis’ brain show

A

caudally-positioned occipital lobe,
lack of a rostrally-located lunate sulcus,

an expanded orbitofrontal cortex.

These features indicate that LB1’s brain was globally reorganized despite its ape-sized cranial capacity (417 cm3)

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14
Q

What does Falk say about floresiensis being microcephalic

A

although the combination of primitive and derived features seen in LB1’s virtual endocast is unique, none of them appear pathological and the most dramatic features (expanded caudal temporal lobes and expanded prefrontal cortices) appear in just those parts of the brain that have recently been recognized as foci of differential selection during the course of human evolution

If Homo floresiensis were a “dwarfed” human weighing 30 kg, its predicted brain size should be 1100 cc.

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15
Q

What does Baab say about floresiensis having Down Syndrome

A

1) often DS symptoms affect soft tissue that cannot be assessed in skeletons
2) features that can be assessed are not present in LB1 eg narrow palate (foudnd in 2/3 humans with DS )
3) the low and poorly filled out cranial vault of LB1 contrasts sharply with samples of both DS and euploid modern humans who are themselves quite similar, and is more similar to H. erectus

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16
Q

Give for and against floresiensis being an australopith

A

a. For: too many primitive features – foot v different to those footprints from 1.5mya)
b. Against: but no fossils from this time in SE Asia reflect this – depends if the fossils are all classed as erectus

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17
Q

What suggest floresiensis may have split from the tree even earlier than erectus

A 
 Morphology of the foot (more primitive than the foot that made the Ileret, East Turkana, Kenya, footprints 1.5 Ma years ago)
 Relatively short, very curved clavicle
 Absence of humeral torsion
 Ape‐like wrist
 Flared iliac blades
 Relatively small lower limb 
articulations
 Relatively short legs
18
Q

Describe island biogeography

A
  • Species diversity declines with distance and island size
  • Islands often have few predators
  • Islands have limited resources and scope for dispersal
  • Large animals get smaller, small animals get bigger
19
Q

Give examples from Flores of the rule that Large animals get smaller, small animals get bigger on islands

A 
GIANT:
Giant marabou 
Leptoptilos sp. nov.
(1.8 m tall)
Rat
Komodo dragon

Dwarf:
stegodon
floresiensis

20
Q

Why does the brain size of floresiensis suggest it is erectus

A

If Homo floresiensis were a “dwarfed” human weighing 30 kg, its predicted brain size should be 1100 cc.

If Homo floresiensis were a “dwarfed” Homo erectus weighing 30 kg, its predicted brain size should be 500‐650 cc.

21
Q

Why do Dwarf hippos help explain floresiensis being early Homo

A

• NORMAL‐SIZE SPECIES: brain mass scales to body mass to the power of 0.75; within spp <0.25, and
closely related spp: 0.2‐0.4

• DWARF HIPPOS: brain mass to body mass allometric relation: 0.35 (after growth completion), 0.47 when
infant growth is included

• Some spp of dwarf hippo have even smaller brain/body ratios

If these unique scaling relations were equivalent in H floresiensis, brain reduction in a small early Homo (such as from Dmanisi) at these rates could explain the brain/body ratio in floresiensis – consistent with
being an island dwarf erectus/habilis

22
Q

Who is the other small bodied hominin (not floresiensis)

Where/when did it exist

A

Homo luzonensis

Callao Cave
 Philippines
 67 Ka

23
Q

How many individuals have been found of Homo luzonensis

A

at least 3 individuals

24
Q

How do the premolars of Homo luzonensis compare to other hominins

A

• Premolars: large in comparison to other Homo

• Upper premolars: 2‐3 roots; mesio‐distally expanded lingual crown, and different EDJ from Homo sapiens, H
erectus and neanderthalensis

• Premolars combine size and shape features of Middle Pleistocene Homo, H. neanderthalensis, H. floresiensis and H. sapiens

25
Q

How do molars of H luzonensis compare to other hominins

What about the enamel-dentine junction shape

A

Molars very small and mesio-distally compressed; M1 >M2 >M3; shape affinities with H. erectus and H sapiens.

• Some EDJ and root features cf Australopithecus and Paranthropus

26
Q

What is interesting about H luzoensis hand phalanges

A

Long and narrow intermediate manual
phalanx (~ to H sapiens)

well‐developed flexor tendon attachments and a strongly developed dorsal beak – shared traits with Australopithecus and H floresiensis

Distal hand phalanx: unlike any hominin known

27
Q

Describe H luzonensis pedal phalanx

A

marked longitudinal curvature
small bicondylar head

~ Australopithecus

28
Q

Which species is H luzonensis most similar to

A

Homo luzonensis shows a unique combination of derived and primitive features, and is unlike any other form of Homo, including florensis, another island species.

29
Q

Where was naledi found

How old

A

Found in rising star cave in south Africa
256kya
At least 15 individuals

30
Q

What are the key holotype features of naledi

A

Very prognathic face, receding frontal bone
large postcanine dentition
absence of chin
465-560cc

31
Q

Comment on naledi’s brain size

A

465-560cc – vvv small for Homo – departs from trend like floresiensis
EQ – using postcrania – similar EQ to australopith

32
Q

How does naledi’s development compare to other hominins

A 
• Development of deciduous dentition: more 
similar to humans than chimpanzees
• Later stages of tooth development: 
combination of human and chimp‐like 
patterns
• M2: erupts late in the sequence, not 
observed in hominins except humans –
prolonged adolescence?
33
Q

How does naledi’s dentition compare to other hominins

What does this suggest about its diet

A

Comparison to Australopithecus and
Paranthropus
• Smaller, but higher‐crowned and more wear‐resistant teeth
• no differences in tooth sharpness or occlusal complexity

foods with similar fracture
mechanical properties as A africanus and Paranthropus robustus, but more
abrasive (dust, grit)
• Probably different dietary niche to early South African hominins

34
Q

What does naledi’s shoulder suggest about its locomotion (4)

A

• pronounced cranially‐oriented glenoid fossa on scapula
• No humeral torsion
• Australopith‐like clavicle
• Positioned superiorly
and laterally on the thorax like australopithecines

CLIMBING ADAPTATIONS

35
Q

How does naledi’s hand compare to sapiens’

A

Derived wrist morphology: ~humans
 Enhanced manual manipulation

• Finger bones: longer and more curved than most australopithecines
 Strong grasping during climbing and suspension

36
Q

What can we learn from naledi’s lower limb

A

Stature: ~143 cm (139 – 148 cm)
Less than 20% sexual dimorphism
Elongated lower limb

37
Q

How do the bones of naledi feet compare to other hominins

A

Medial cuneiform: similar to humans

calcaneus: closer to apes

38
Q

What is strange (or interesting!) about the age of Homo naledi?

A

Morphological age should be 900kya BUT actually – 236-335kya: relic of old human

(Dembo, 2016)

39
Q

Give a summary of homo naledi

giving location, age, cc/EQ, weight/height, variability, locomotion, diet

A 
Homo naledi
• 256‐335 Ka
• Rising Star cave system, 
South Africa
• 512 cc [465‐560 cc]
• EQ ~ Australopithecus
• 38 kg
• 143 cm tall
• Small variability
• Reduced sexual dimorphism
• Ape‐like shoulders
• Hands adapted for both manipulation and 
 grasping/suspension
• Legs longer than arms
• Lower limb anatomy: walking, but not running
• Diet including hard objects/grit, causing dental chipping
40
Q

Does H floresiensis have any descendants ?

A

extant pygmy population (av height ~ 145cm) of Flores claim to be

but genetic analysis shows their DNA had admixture with N and D but no other unknown hominin DNA

bear signatures of positive selection on FADS - adaptation to island living and diet

suggests multiple dwarfism events can occur

41
Q

Give 4 ecological driving factors for island syndrome

A

Reduced predation.
Reduced biodiversity.
Reduced sexual selection.
Reduced parasite diversity.

42
Q

Why does H floresiensis’ brain suggest it is NOT a human pygmy

A

LB1 scales to an Australopith body:brain ratio, unlike modern human pygmies who have slightly larger heads than predicted as they map onto an allometric scale of ontogeny

Human Evolution (16 decks)

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