Origins of Homo Flashcards
s.l. and s.s.
Homo habilis sensu lato (s.l., broad sense)
Homo habilis sensu stricto (s.s., narrow sense) + Homo rudolfensis + other specimens without clear attribution
Major evolutionary trends at 2.5mya - Paranthropus
Hypermasticatory complex
Increase in cheek tooth size
Body size similar to Australopithecus
Major evolutionary trends at 2.5mya - Homo
Increase in brain size and capacity for tool making
Decrease in prognathism, and postcanine tooth size
Increase in body size
Earliest Homo fossil
Ledi-Geraru left hemimandible, discovered 2015
2.8mya, Ethiopia
Smaller third molar and other traits indicate affinity with Homo. Assigned to Homo genus but no particular species.
Affinity with Homo has been contested based on alleged similarity with Au. sediba.
Homo habilis - temporal range, holotype, sites
2.4-1.4mya
OH 7 mandible, parietals, and hand bones
Sites: Olduvai, Tanzania Koobi Fora, Kenya Omo, Ethiopia Hadar, Ethiopia Sterkfontein, South Africa Swartkrans, South Africa Drimolen, South Africa
Homo derived traits vs. Australopithecus - cranium
Rounded cranial vault Vertical forehead Reduced cranial crests More anterior foramen magnum Reduced prognathism Increased brain size both absolutely and relativel to body size
Homo derived traits vs. Australopithecus - dental
Reduction in postcranine tooth size
Smaller canines
Parabolic dental arcade
OH 7
Homo habilis, Olduvai, Tanzania
2 parietals, juvenile mandible, finger bones
U shaped dental arcade
730-830cc
-> brain enlargement and dental reduction were not linked in hominin evolution
Meets Le Gros Clark’s criteria for Homo
Larger brain - 687cc Capable of language Relatively small teeth Capacity for precision grip Associated with stone tools
Homo habilis vs. australopiths
Similarly small brain size Less projected face Narrow lower face Incipient supraorbital ridge Bell-shaped vault from rear Smaller molars Parabolic dental arcade Flexed basicranium
Homo habilis vs Homo ergaster
Smaller brain Vertical face in both Narrow lower face Less developed supraorbital ridge No bell shape in H. ergaster Similarly small molars Parabolic dental arcade Flexed basicranium
OH 62
Olduvai, Tanzania, 1.8mya
Individual with a reliable association of cranial and postcranial remains.
Craniodental anatomy similar to other H. habilis
Body size and proportions similar to Australopithecus
Derived H. erectus skeleton 1.6mya -> rapid postcranial evolution? OH62 not H. habilis? H. habilis not ancestral to H. erectus? H. habilis and H. erectus overlap and fill different niches?
KNM-ER 1813
Homo habilis, Koobi Fora, Kenya
Small brain - 510cc - below alleged limit for Homo
Small teeth
Narrower face
Homo-like face
SK 847, SK 15, Stw 53
Homo habilis, South Africa
<2mya
Small teeth and general gracility
Traditionally put into H. habilis, but taxonomic affinities are uncertain
AL 666-1
Homo habilis, Hadar, Ethiopia
2.33mya
With stone tools
Similar to Olduvai material
KNM-ER 1470
H. rudolfensis (H. habilis s.l.), Koobi Fora, Kenya
Australopithecus-like face
Homo-sized brain
KNM-ER 1813 (H. habilis s.s.) vs KNM-ER 1470 (H. rudolfensis)
KNM-ER 1470 has:
- bigger brain - 775cc
- more facial projection
- broad midface - Au.-like
- bigger molars
- slight browridge
- well developed mandible for chewing muscles
KNM-ER 1813 has:
- incipient supraorbital ridge
- relatively smaller brain size - 612cc
- broader upper face than midface
- smaller molars
- less robust mandible
Variation between H. habilis s.s. and H. rudolfensis
Extreme forms are easy to differentiate but intermediate forms are not easily classifiable.
Co-efficient of variation (CV) - measures variation in a sample.
CV = standard deviation/mean x100
H. habilis s.l. - 12.4 Compared to: Gorilla 10.9 H. sapiens 10.1 Bonobo 9.5 Chimpanzee 8.9
Greater than gorillas - an extremely dimorphic group. H. habilis unlikely to have been as dimorphic as gorillas = two different species.
Homo rudolfensis - temporal range, holotype, sites
2.4-1.6mya
Holotype - KNM-ER 1470
Sites:
Koobi Fora, Kenya
Uraha, Malawi
Homo rudolfensis - morphology
Face is widest in its midpart (compared to superiorly in H. habilis)
Larger absolute brain size
Robust jaws, large postcanine teeth, complex premolar root systems
Body size ~45kg
KNM-ER 1470
H. rudolfensis, ~1.9mya
Large, rounded brain case
Initially placed into H. habilis
UR 501
Malawi, 2.5-2.3mya
Very robust mandible
Connects East African and South African Homo
Possibly H. rudolfensis
Homo or Australopithecus habilis?
Brain size = 650cc, between Australopithecus 400-550cc & H. ergaster 730-1070cc.
Body weight - M 52kg, F 32kg Whereas: A. afarensis - M 45kg, F 29kg H. erectus - M 63kg, F 52kg H sapiens - M 68kg, F 62kg
Australopithecus-like features e.g. body size, shape, locomotion, jaws & teeth, development, brain size (Wood & Collard 1999)
OH 7 hand & OH 62 skeleton show climbing features = different adaptive niche to later Homo
Encephalisation Quotient
Measure of relative brain size. Ratio of actual brain mass and predicted brain mass.
Pan troglodytes 2.8-3.1 Australopithecus 2.4-3.3 H. habilis 4.3 H. erectus 4.4 H. sapiens 7.2
Why are OH fossils placed within the genus Homo?
Slightly larger brain than Australopithecus
Slightly smaller posterior teeth
Habitual erect posture and bipedal gait
H. sapiens-like foot bones
Different affinities in hand bones, but capable of making tools
Differences between Australopithecus and Homo
Homo has: Increased cranial capacity Reduced prognathism Reduced teeth and parabolic arcade Obliged and modern bipedalism Sophisticated and more committed use of stone tools More complex social behaviour Increased meat consumption
Brain size and diet
~2mya - substantial increase in brain size begins
Systematic hunting & increased meat consumption
Advantages of meat:
Higher energetic contents
Easier digestion (expensive tissue hypothesis)
Disadvantages of meat:
Harder to get & competition
Requires planning, co-operation, complex social networks
Expensive tissue hypothesis
Aiello & Wheeler 1995 -> humans cannot afford having a big brain together with other ‘expensive tissues’
Trade-off = brain size increases and gut size decreases
Associated with higher quality diet (more meat, perhaps cooked)
HOWEVER:
sample of 100 mammalian species -> no significant relationship between brain size and gut size
Brain size is negatively correlated only with the size of adipose deposits
Encephalisation and fat storage are alternative strategies to buffer against starvation
H. habilis and stone tools
Oldowan industry - thought to be the most primitive human technology for many years. Associated with OH 7 at 1.8mya
Concoidal fractures
Manuports - rocks moved by hominins but not worked
Hammerstones - used to remove flakes from other rocks
Core forms - pebbles which flakes were removed or used as tools themselves
Flakes
Demonstrate advanced knowledge of the mechanical properties of stone
Pre-Oldowan stone tools
Tools in Gona, Afar, Ethiopia at 2.6mya
Cutmarks in Bouri at 2.5mya - association with Au. garhi? Lack of associated lithics suggests curation of tools
Cutmarks in Dikika, Ethiopia at 3.39mya - Dominguez-Rodrigo et al 2010 “In a less contentious context, the marks would likely be accepted as genuine cutmarks.”
Stone tools at Lake Turkana, Kenya, at 3.3mya
Lomekwian stone tools
West Turkana, Kenya, 3.3mya
Same location as Kenyanthropus platyops
Predates Oldowan by 700,000 years - possibly the oldest human technology
Simplest mode to make stone tools
Very large and crude
Human-like dexterity is not required
Tool use in non-human primates
Chimpanzees, macaques, capuchins use stones to open nuts and crabs
Therefore tool use is NOT a defining trait of the genus Homo - not surprising that Australopithecus used tools as well
Did other hominins make or use stone tools?
OH 5 (P. boisei) found in layers with stone tools
Stone tools found at SK Mbr 3, only with P. robustus
P. robustus hand bones capable of a modern human-like precision grip
Co-operative hunting
Hunting in groups = division of labour and role specialisation
Implies higher cognitive abilities and communication
80-95% of carnivores are solitary
Exceptions: lions, wild dogs, spotted hyenas, chimpanzees, humans
OH 8
Homo habilis foot
Adducted hallux
Straight - not curved - metatarsals
Evidence for transverse and longitudinal arch
Could also belong to P. boisei
Modern features have been contested
Palaeolithic era
2.3mya to 12,000 years ago
Divided into:
Lower Palaeolithic 2.3mya to 125,000 years ago
Middle Palaeolithic 125,000 to 35,000 years ago
Upper palaeolithic 35,000 to 12,000 years ago
Lower Palaeolithic stone tools
Oldowan and Acheulean
Oldowan: opportunistic flaking. Associated with hunting behaviours, but likely useful for other activities e.g. digging, woodwork, defence.
Acheulean: first appeared 1.4mya. Characteristic tool is the hand axe, plus tool types specific to certain regions. Evidence for preconceived notion of what the tool should look like = greater intellectual capacity.
Homo naledi
Rising Star cave system near Johannesburg, South Africa. 1,500 fossils (Berger et al., 2015)
Combination of primitive and derived characteristics:
Curved fingers
Primitive shoulders
465-560cc brain size
Premolar asymmetry
Increased size of teeth towards the back of the tooth row
