Small bodied hominins Flashcards
How old is the Homo floresiensis material?
cc?
How tall?
From Flores, Indonesia – 60-100kya
417cc,
106cm tall
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
What is strange about the P3 of Homo floresiensis?
very large
Longer AP than basolaterally – unseen before
Size and weight of floresiensis
106cm, 30kg
- Comment on the robusticity of Homo floresiensis jaw:
Very robust for its body size – seen in corpus and symphyseal robustity
What are the derived/ humanlike bipedal traits of H floresiensis
• Hallux: adducted
• Arches: plantar
Efficient biped
Primitive traits found throughout skeleton
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)
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
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
What are the different options for what floresiensis is (5)
- Pygmy H. erectus
- Microcephalic pathological modern human
- H. habilis
- Australopithecine
- None of the above
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)
What is Laron Syndrome
primary or classical GH insensitiv-ity or resistance)
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)
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.
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
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
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
