Pleistocene Hominins Flashcards
Describe australopithecine dentition generally
Australopithecines have
• reduced anterior dentition in comparison to African apes
• relatively large molars
How much time do chimps spend feeding
Chimps spend ~ 50% of each day feeding
What is Tm
How is it calculated
Torque (Tm): the force a muscle produces around a joint
Tm = Fm * lever arm
Fm= contractile force of muscle (proportional to its cross‐sectional area)
Lever arm= perpendicular distance between the muscle’s line of action and the centre of rotation
Fr = the vector sum of all the separate muscle forces
What is Tb
How is it calculated
Torque (Tb): the force a bite produces
Tb = Fb * load arm
Fb= bite force (= Fr * Fr lever arm/load arm)
Load arm= perpendicular distance between bite force vector and centre of rotation
What is mechanical advantage
MA: muscle’s mechanical advantage measures the efficiency of torque generation (bite force per
contraction; trade‐off with angular velocity)
MA = lever arm/load arm length
What species are in the Paranthropus genus
†P. aethiopicus
†P. robustus
†P. boisei
What species is the Black Skull from
What was it originally thought to be from
When is the skull dated to
Paranthropus aethiopicus
originally named Australopithecus
boisei
• Dated to 2.5 Ma
Why was the species P aethiopicus revived
Similarities between the Omo 18 mandible, and the
two fossils from West Turkana (KNM‐WT 17000 and
KNM‐WT 16005) led to the reviving of the species
aethiopicus
What are the sites and dates of the fossils of P. aethiopicus
• Omo, Shungura, Members C to F, Ethiopia (2.7‐
2.3 Ma)
• oldest fossil: L55s‐33 mandible fragment from level C6, Omo, 2.7 Ma
• Lomekwi, West Turkana, Kenya (2.5‐2.35 Ma)
• Laetoli, Tanzania (2.7‐2.5 Ma)
Describe the Black Skull (7)
What species is this
FM?
- cranial capacity 410 cc
- Long, flat cranial base
- > sagittal orientation of the petrous bone
- Very large nuchal muscles, oriented vertically
- Very large sagittal crest
- Large, very prognathic face
- anterior position of root of zygomatic arches
Paranthropus aethiopicus
more medial FM
How do the bones of the black skull demonstrate the efficacy of Paranthropus aethiopicus’ mastication
Flaring zygomatics inverted inferiorly – massive attachment for masseter, high sagittal crest, small vault, prognathic face – huge temporal fossa – for huge temporalis from here and sagittal/ nuchal crest, bar like supraorbital torus, disproportionately maxilla with huge sockets for molar and premolars
Increased mechanical advantage based on the improved lever positions of the muscles, anterior position of z arches puts masseter more forward (lengthening lever arm in sagittal plane)
All post canine teeth v large
Prognathicism would limit masticatory efficiency
Have any juvenile aethiopicus fossils been found
L 338y‐6 juvenile cranium • ~ 10 yrs old? • 420‐440 cc • Omo Shungura, Member E, Unit E‐3 • 2.4 – 2.3 Ma
- How do the fossil records of aethiopicus and boisei compare?
- Most fossils: boisei
* Fewest fossils: aethiopicus
What was the first fossil (type specimen) of boisei
OH 5, Olduvai Gorge ~ 1.8 Ma discovered in 1959 by Mary Leakey Paranthropus boisei Previous names: Zinjanthropus boisei Australopithecus boisei
Give the key features of P boisei fossil KNM-ER 406 from the front
KNM-ER 406
510cc
Flared zygomatics
Sagittal crest
Flat face
High nuchal crest tilted up, different to OH5
Distinct morphology between these fossils
What is the cc of boisei
510cc
Describe the inferior features of the boisei skull
Nuchal crest projects down instead of out – massive nuchal musculature
Massive palate
Big temporal fossa
Molarised premolars
Reduced anterior dentition
Much bigger mandibles that australopithecius
Why does the boisei fossil from Konso differ from other specimens
1.4 Ma
Dry grassland environment
Different combination of the typical “robust” features:
• Configuration of sagittal crest like P. aethiopicus
• Broad and short palate, unlike other boisei
• Less concave face‐zygomatic complex than other boisei
Why might boisei be considered (one of) the most successful hominins?
Long lasting 2.3-1.1/1.2 ma
Does boisei fossils display sexual dimorphism
KNM-ER 732 is smaller than 406 but similar cc
No sagittal crest in 732
consistent dimorphism between males and females with african apes but less than in gorillas or mandrills
How does boisei cc compare to aethiopicus
increasing brain size in boisei
What features of KNM-ER 406 are repeated in other fossils from Koobi Fora?
What does this suggest -
KNM-ER13750 23000 show similar medial depression in arched supraorbital torus
extremely flared zygomatics
population level variation
What is important about Konso boisei fossils
Konso is most northern location where boisei is found, also very recent 1.4mya
different to other boisei -
• Broad and short palate, unlike other boisei
• Less concave face‐zygomatic complex than other boisei
suggests variation in time or space
Why is it difficult to be sure of Paranthropus boisei’s stature
only a few elated fossils have been found eg OH80 femur
because Paranthropus is contemporaneous with Homo it is difficult to know who it belongs to
What is the estimated size of boisei stature
Give the study that worked out these estimates
Extrapolation from the size of linea aspera of the
OH 80 femur (using regression formulae for H.
sapiens femur‐stature patterns):
• Femoral length ~ 400 mm
• Estimated ≥ stature: 156 ± 3.91 cm
• Estimated weight: between 50 – 61.7 kg
Dominguez‐Rodrigo M et al. 2013
What is interesting about the OH80 radius
most robust hominin forearm known
foveae seem similar to great apes - climbing adaptations?
What are the key robust adaptations of boisei (5)
flaring of zygomatics pronounced post‐orbital constriction sagittal and nuchal crests massive mandible Orthognathic, concave face
most extreme morphology of robust hominins
Give the megadont features of boisei (3)
Hyper‐megadont
very thick enamel
molarised premolars
small anterior dentition
Why can robustus, like boisei, be considered a “successful” hominin?
Robustus is the only Paranthropus in south Africa - 2ma to 1ma – lived for at least a million years – uncertainty about when it went extinct
Where is the richest fossil record of Paranthropus
Swartkrans is richest fossil record of Paranthropus – has oldest and most recent fossils – complex stratigraphy
What does “premolar molarization” mean?
Premolars developing molar characteristics
How does the temporal fossae of robustus compare to boisei
Larger than austrolapithecus but smaller than boisei
What was Paranthropus robustus’ cranial capacity?
475-530cc
Describe the face of SK48
P robustus
small flat face with laterally flaring zygomatics
Enormous palate and posterior dentition
Why is DNH 155 interesting?
(P robustus)
larger than DNH7 with unique features
eg alveolar prognathism and No “zygomaticomaxillary step”
How is sexual dimorphism expressed in Paranthropus robustus?
Very few fossils so hard
absent sagittal crest
Size difference:
McHenry 1991
F:110 cm
M:132 cm
Grabowski et al. 2015
(based on 9 femoral fragments)
F:~ 24 kg
M:~ 32 kg
What was Paranthropus robustus’ locomotor strategy? How do we know?
Trabecular bone patterns of femoral head– adapt to habitual weight loading on skeleton
Similar to living apes – frequently used highly flexed hips in climbing
Give key robust features of Paranthropus robustus
Orthognathic, concave face, with strong maxillary pillars
Flaring zygomatics Cranial cresting Large molars, molarised premolars Post‐orbital constriction Large to massive mandible
Did Paranthropus have an effect on the environment
Tools have been found at these areas and suggestions of fire use – cannot be attributed to homo or Paranthropus but either way would affect environment about them
bones found which were burnt at temperature of a campfire
- How does boisei mandibular morphology compare to that of a) other great apes and b) other species of Paranthropus?
a) Mandible is disproportionally large for body size – extreme in robustus and boisei – have a widening and deepening of mandible
b) boisei is more robust than robustus
- How does boisei post canine dentition morphology compare to that of a) other great apes and b) other species of Paranthropus?
For all teeth but M1 follow early trend set by earlier hominins, boisei departs from this (bigger larger than expected) , while robustus continues trend
What are fallback foods
Needed strength to shift diet to harder foods – low nutritional value, but important when preferred food is scarce
What is Liem’s paradox
extreme adaptations emerge to withstand the most challenging
aspect of an organism’s ecology, rather than the most common aspect
Give an example of Liem’s paradox in primates
Theropithecus gelada (has large, thick enamel):
• predominantly feeds on grasses, but shifts to tougher
underground storage organs (USOs – tubers, corms and
roots) during the dry season
How might fallback foods explain Paranthropus morphology?
Fall back foods drive anatomical adaptations for food processing while high quality foods drive behavioural adaptations for harvesting
Unique eco niche of Paranthropus – needed to eat hard (staple diet) or required lots of chewing as low quality (fall back foods)
How does a diet of leaves show up on tooth microwear
those who feed on leaves tend to exhibit fine paralleled scratches • those who feed on hard objects tend to show complex or pitted patterns
How does the diet of africanus differ from robustus
P. robustus: higher values for 11 attributes related to feature complexity, size, and depth (rougher, larger, deeper features) • Au. africanus: smoother, simple surfaces, with smaller, shallower, more aligned features
Peterson (2018)
How do diets differ between P robustus populations
P. robustus from Swartkrans and
Drimolen show similar degrees
and patterns of microwear texture
What does the microwear of boisei teeth show
relatively low complexity and anisotropy values. This suggests that none of the individuals consumed especially hard or tough foods in the days before they died.
The apparent discrepancy between microwear and functional anatomy is consistent with the idea that P. boisei presents a hominin example of Liem’s Paradox
What are C3 and C4 foods
- C3: low C13 value – all tree and bush biomass in African savannahs + herbaceous species
- C4: tropical grasses and sedges
How do we know the diet of Paranthropus robustus varied seasonally?
Laser ablation sampling – isotope ratio varies while the teeth grew, when children, c13 low (C3) – seasonally variable , flexible diet
What does isotope analysis of boisei and robustus show about their diets - what animals are their diets similar to
boisei Similar food to zebras and hippo
Robustus was closer to other hominins, boisei is specialized with high % of C4 grasses/sedges
What were the % of C4 plants in boisei and robustus diets
boisei: ≥ 75‐80% C4 plants – dominated by grasses and sedges
robustus: 30‐40% C4 plants
What do we know about aethiopicus’ diet
Early and late aethiopicus did not eat the same foods
OH5 vs KNM-ER 406: different cranial capacity and different face proportion so different masticatory mechanical advantage
• ISOTOPES: shift from mainly C3 to mainly C4 plants after 2.37 Ma
Summarise the morphology and diet of aethiopicus
Paranthropus aethiopicus
• MORPHOLOGY: less efficient masticatory adaptation (very prognathic)
than boisei or robustus
• ISOTOPES: shift from mainly C3 to mainly C4 plants after 2.37 Ma
Summarise the morphology and diet of boisei
• MORPHOLOGY: adaptations to hard object (nuts, seeds) processing
• MICROWEAR & ISOTOPES: prolonged masticatory bouts involving tough, abrasive C4 plants
• DIET: high % of C4 grasses, or sedges or their combination
• Potential role of fallback hard object foods in driving extreme
morphology unclear
Summarise the morphology and diet of robustus
• MORPHOLOGY: adaptations to hard object (nuts, seeds) processing
• MICROWEAR: diet regularly included hard objects
• ISOTOPES: similar to Au. africanus, 30‐40 % C3‐C4 plants
• DIET: fruits, nuts; diet varied seasonally and ontogentically
• Potential role of fallback hard object foods in driving extreme
morphology probable; termites dug with bone tools?
Give key differences between aethiopicus and boisei
brain size:
aethiopicus=410cc
boisei=550cc
boisei is generally the most robust of all robust hominins - this could be degrees of expression But difference in diet and fall back foods suggest different eco niches
But difference in diet and fall back foods suggest different eco niches (3)
Using primatology cf gelada eg and using morphological analysis – allows some reconstruction but doesn’t shed too much light on dietary variation and convergence can be a problem
Dental microwear texture analysis – leaf eaters display parallel scratches hile hard object eaters show complex or pitted patterns
Stable isotope – C3 vs C4 – more suggestive of area and specific about what type of vegetation was eaten, reaveals seasonality and variation
Laser ablation sampling – isotope ratio varies while the teeth grew, when children
Why is it argued that robusts should be sunk into the Australopithecine genus
Authors eg Tobias have said Paranthropus is a superspecies within the Australopithecine genus and australopiths were allometrically “ scaledvariants ” of the same morphotype
What did Kimbel find regarding Paranthropine monophyly
Strait and Grine (2004)combined 109 non-metrical traits with 89 traits based on linear measurements and, using two differently composed in-groups, also found that the three “robust ” taxa (P. robus-tus, P. boisei
and P. aethiopicus) consistently formed a monophyletic group, result also reached by the cladistic analysis by Kimbel et al. (2004).
What did Gunz find regarding the skull of robustus
Gunz et al.(2012) showed that a P. robustus
cranium, SK 48, is morelikely to be a scaled variant of P. boisei
than a scaled variant of
A. africanus - supports idea of a robust clade
Why is there a good case for robust similarities just being homoplasy
Phylogenetic studies of bovids (Gatesy et al. 1997), hippos, carnivores, Old World monkeys, elephants and equids all suggest that the evolutionary history of these groups shows evidence of substantial homoplasy during the period of time spanned by the megadont and hyper-megadont hominins.
many, but by no means all, of the characters that link
Paranthropus taxa in the same clade are related to the masticatory system. These are likely to be functionally integrated, thus potentially they are non-independent and if so, they should not be coded as individual independent characters in a cladistic analysis
the faces of
Kenyanthropus platyops and Homo rudolfensis
are, like P. boisei, both orthognathic relative to earlier hominins, but whereas the former have small or moderately sized postcanine teeth thelatter shows extreme postcanine megadontia. Since
K. platyops
and
H. rudolfensis
are generally not considered tobe closely-related to
P. boisei
, the cited similarities amongthese taxa must be due to homoplasy
What did Turner and Wood suggest about Paranthropus monophyly
Turner and Wood (1993) assessed the probability of monophyly by examining the
biogeographic patterns of African Plio-Pleistocene large mammals. They concluded that during the time range of Paranthropus ,there was evidence in at least one mammalian group of faunal dispersal between regions, with several monophyletic groups having representatives in both regions -> lends credibility to the hypothesis of
Paranthropus monophyly
What is a genus?
Generic classification in biology today, above species and below family representing:
• a group of monophyletic species
• reflect a distinct ecological niche that shapes the
evolutionary trajectory of the descendant species
How was Homo defined in late 18th Century
late 18th C: Blumenbach definition of Homo sapiens ‐ small canines, chin, short
mandible and face, large rounded skull, bipedalism
1856: discovery of the 1st Neanderthal at Feldhofer, Germany – arguments
whether it should be H sapiens or a new species H neanderthalensis. Independent of the
view, expanded the concept of Homo beyond Homo sapiens
How was the definition of Homo changed in the 20th Century
mid‐20th C: Homo as an adaptation, not morphology
Dobzhanski argued that culture allowed hominins to adapt to all ecological niches, so the human lineage had no speciation
Mayr argued that bipedalism unified all hominin species as distinct from
apes into a single ecological niche, and should therefore all be classified as
Homo
What happened in 1964
Leakey and colleagues name a new species, Homo habilis, from Olduvai
Gorge – brain size rubicon and stone‐tool manufacture [Oakley 1949 publishes
Man the Toolmaker]
Who was included in Homo in 18-19th C
What was the defining morphology
Sapiens
Eventually neanderthalensis
Pilthecanthropus erectus
small canines, chin, short
mandible and face, large rounded skull, bipedalism
What did Mayr argue about who should be included in Homo
Mayr argued that bipedalism unified all hominin species as distinct from apes into a single ecological niche, and should therefore all be classified as
Homo
Where were the first fossils of Homo habilis found? What non-Homo species did they coexist with?
Olduvai Gorge – Jonny’s child OH7
Presumed association with the stone tools found at gorge and larger brain
Co-existed with boisei
The below traits did not develop as a package
What are the diagnosing features of Homo (14)
- Bipedalism
- A fully opposable, well‐developed thumb capable of a precision grip
- a larger cranial capacity than in australopithecines, above 600 cc
- No sagittal crests
- Reduced to absent post‐orbital constriction
- Variable supraorbital torus development
- Variable degrees of facial prognathism, but no concave facial morphology (as
seen in boisei) - Variable chin development – from absent to well‐formed
- Bicuspid P3
- Molars smaller, in average, than in australopithecines
- Upper 3rd molars, in general, smaller than 2nd upper molars, which are in
general, smaller than 1st molars - Lower 3rd molars that can be significantly larger than 2nd molars
- Small incisiform canines
- No molarisation of premolars
What are the key differences between the skull of Habilis and sapiens
No flaring zygomatics and no postorbital constriction, but larger mouth than sapiens like robustus but smaller teeth and non molarised premolars
How big is the habilis brain
How does the skull appear (4)
510cc
Rounded vault, without crests Round small supraorbital torus, with a medially depressed glabella Small dentition Small third molar and bicuspid premolar
What did the virtual reconstructions of OH7
What is the age of this fossil
OH7=”Johnny’s Child”, habilis
large endocranial volume – 729‐824 cc
1.84mya
Where are fossils of Homo habilis found?
E Africa: Olduvia gorge, Tanzania and Koobi Fora, Turkana Basin, Kenya
Sterkfontein? – contentious
Temporal range of habilis?
2.31 million years ago to 1.65 million years ago (mya).
Give the following for habilis
• Body size:
• Cranial capacity:
- Dentition:
- Cranial morphology:
- Body size: 30-42kg
- Cranial capacity: 590-730cc
- Dentition: reduced post canine dentition
- Cranial morphology: non cresting and reduced post orbital constriction
Which taxon was rudolfensis originally put into
H. habilis
because of its
large cranial capacity.
differences with habilis originally attributed to sexual dimorphism
