Small bodied hominins Flashcards by Jade Rayquaza

How old is the Homo floresiensis material?

cc?

How tall?

From Flores, Indonesia – 60-100kya

417cc,

106cm tall

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What are the key features of the Homo floresiensis skull

 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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What is strange about the P3 of Homo floresiensis?

very large

Longer AP than basolaterally – unseen before

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Size and weight of floresiensis

106cm, 30kg

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Comment on the robusticity of Homo floresiensis jaw:

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

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What are the derived/ humanlike bipedal traits of H floresiensis

• Hallux: adducted

• Arches: plantar
Efficient biped
Primitive traits found throughout skeleton

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What are the unique bipedal traits of floresiensis

• 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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Did H floresiensis make tools

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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When did H floresiensis go extinct

What happens in Flores after this

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

Pygmy H. erectus
Microcephalic pathological modern human
H. habilis
Australopithecine
None of the above

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

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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What is Laron Syndrome

primary or classical GH insensitiv-ity or resistance)

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What derived features does floresiensis’ brain show

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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What does Falk say about floresiensis being microcephalic

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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What does Baab say about floresiensis having Down Syndrome

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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Give for and against floresiensis being an australopith

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

 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

Describe island biogeography

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

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

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

Dwarf:
stegodon
floresiensis

Why does the brain size of floresiensis suggest it is erectus

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.

Why do Dwarf hippos help explain floresiensis being early Homo

• 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

Who is the other small bodied hominin (not floresiensis)

Where/when did it exist

Homo luzonensis

Callao Cave
 Philippines
 67 Ka

How many individuals have been found of Homo luzonensis

at least 3 individuals

How do the premolars of Homo luzonensis compare to other hominins

• 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

How do molars of H luzonensis compare to other hominins What about the enamel-dentine junction shape

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

What is interesting about H luzoensis hand phalanges

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

Describe H luzonensis pedal phalanx

marked longitudinal curvature small bicondylar head ~ Australopithecus

Which species is H luzonensis most similar to

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

Where was naledi found How old

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

What are the key holotype features of naledi

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

Comment on naledi's brain size

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

How does naledi's development compare to other hominins

``` • 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? ```

How does naledi's dentition compare to other hominins What does this suggest about its diet

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

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

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

How does naledi's hand compare to sapiens'

Derived wrist morphology: ~humans  Enhanced manual manipulation • Finger bones: longer and more curved than most australopithecines  Strong grasping during climbing and suspension

What can we learn from naledi's lower limb

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

How do the bones of naledi feet compare to other hominins

Medial cuneiform: similar to humans calcaneus: closer to apes

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

Morphological age should be 900kya BUT actually – 236-335kya: relic of old human (Dembo, 2016)

Give a summary of homo naledi giving location, age, cc/EQ, weight/height, variability, locomotion, diet

``` 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 ```

Does H floresiensis have any descendants ?

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

Give 4 ecological driving factors for island syndrome

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

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

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