Homo Habilis (Handy Man)
-2.1 and 1.5 million years ago
-Jawbone fragment intermediate between Australopithecus and H. habilis dated to 2.8 million years ago reported in 2013.
-Louis and Mary Leakey (Olduvai Gorge in Tanzania - 1960-1963).
-Suspected that it was this slightly larger-brained early human that made the thousands of stone tools also found at Olduvai Gorge.
Short stature - 1.3m (4ft 3 in) tall.
-Disproportionately long arms compared to modern humans.
-Less prognathic than australopithecines from which it is thought to have descended.
-Cranial capacity slightly less than half of the size of modern humans.
-Often been thought to be the ancestor of the more gracile Homo ergaster, which in turn gave rise to the more human-appearing species, Homo erectus.
-Cranial capacity ca. 640cm³ was on average 50% larger than australopithecines, but considerably smaller than the 1350 to 1450cm³ range of modern Homo sapiens.
Homo ergaster
- 1.9million and 1.4MYA (early Pleistocene).
- Thought to be ancestral to, or as sharing a common ancestor with, or as being the same species as, Homo erectus.
- Interpreting Homo ergaster inevitably leads to Homo erectus, particularly regarding the taxonomy issues that persist within the scientific community of classifying the two species and separating their two lineages—if indeed they represent two separate lineages.
Features separating ergaster from earlier non-Homo species:
- Reduced sexual dimorphism,
- Smaller, more orthognathous face,
- Smaller dental arcade,
- Larger cranial capacity (700–900cm³ in earlier specimens, and 900–1100 in later specimens).
- Remains have been found in Tanzania, Ethiopia, Kenya, and South Africa.
Features separating ergaster from erectus
- H. ergaster may be distinguished from H. erectus by -thinner skull-bones and lack of an obvious supraorbital foramen.
- H. ergaster may be distinguished from H. heidelbergensis by its thinner bones, more protrusive face, and lower forehead.
Homo erectus
- 1.9 MYA to 70,000 years ago (Pleistocene).
- H. erectus originated in Africa and spread from there, migrating throughout Eurasia as far as Georgia, India, Sri Lanka, China and Indonesia.
- Approx. 1.79m - only 17% modern male humans are taller - and were very slender, with long arms and legs.
- Cranial capacity greater than that of Homo habilis (although Dmanisi specimens have distinctively small crania): earliest fossils show a cranial capacity of 850cm³, while later Javan specimens measure up to 1100cm³, overlapping that of H. sapiens
- Frontal bone is less sloped
- Dental arcade smaller than that of the australopithecines
- Face is more orthognatic than either australopithecines or H. habilis
- Large brow-ridges
- Less prominent zygomata (cheekbones).
- Sexual dimorphism in H. erectus—males are about 25% larger than females—is slightly greater than seen in the later H. sapiens, but less than that of the earlier genus Australopithecus.
Origin of homo erectus?
- Debate also continues about the classification, ancestry, and progeny of Homo erectus, especially vis-à-vis Homo ergaster, with two major positions:
1) H. erectus is the same species as H. ergaster, and thereby H. erectus is a direct ancestor of the later hominins including Homo heidelbergensis, Homo neanderthalensis, and Homo sapiens; or,
2) it is in fact an Asian species distinct from African H. ergaster.
3) H. ergaster an “African variety”, of H. erectus, and they offer the labels “Homo erectus sensu stricto” (strict sense) for the Asian species and “Homo erectus sensu lato” (broad sense) for the greater species comprising both Asian and African populations.
4) Considering the large morphological variation among all Dmanisi skulls, researchers now suggest that several early human ancestors variously classified, for example, as Homo ergaster, or Homo rudolfensis, and perhaps even Homo habilis, should instead be designated as Homo erectus.
Homo heidelbergensis
-Late surviving Homo erectus, or a separate species?
-Term used to describe some African, European and Asian specimens c450-180k BP
-Difficult to date, difficult to define
-Common ancestor of Neanderthals and modern humans?
-Combines primitive and derived traits:
projecting supraorbital torus, thick cranial bones
endocranial capacity >1200cc, steep frontal, rounded occipital
-Type specimen: Mauer mandible (Heidelberg, Germany)
-400-500Ky
-Very broad ramus
-Molars smaller than H. erectus
-Primitive non-projecting chin
Homo neanderthalensis
-Discovered 1856 in a quarry, Feldhofer grotto, in the Neander Valley, Germany.
Neanderthal cranium
- endocranial capacity 1245-1740cc
- long, low vault
- midparietal max breadth
- low receding frontal
- continuous supraorbital torus
- occipital bun
- small mastoid process
- flat skull base
- long prognathous face
- large nasal cavity
- receding zygomas
- thick maxilla
- retromolar space
Neanderthal post crania
- horizontal, robust cervical vertebrae
- thick, rounded ribs
- large muscle & ligament attachments
- Cortical bone thick, no pilaster (ridge) on femur
- Distal phalanx of thumb equal length to proximal phalanx
- Femur shafts bowed
Significance of Neanderthal Anatomical Features?
- Reproductive implications:
- Longer pubis – larger pelvic inlet – longer gestation?
- Adaptation to cold environment:
- Short thorax, short limbs, short fingers
- Broad nose
- Differences in posture & locomotion:
- Arm musculature
- Hand anatomy
- Thigh musculature
AMH: Anatomically Modern Humans Crania
- endocranial capacity usually >1350cc
- vertical frontal
- high cranial vault
- parietal bossing
- rounded occipital (no torus)
- variable, gracile, supraorbital torus
- flat face
- canine fossa
- variably robust mandible
- chin
- no retromolar space
Anatomically Modern Humans Post Crania
- Decreased overall robusticity
- Ventral sulcus (groove) of scapula
- Dorsal sulcus in Neanderthals
- Distal phalange of thumb 2/3 length of proximal
- Small apical tuberosities on distal phalanges
- Thin cortical bone of femur and tibia
- Pubis short and thick
- Illiac blades twisted inwards
- Sacrum pushed back
Significance of AMH morphological features?
- Some may reflect increased tool use:
- Relatively flat face – less use of teeth as tools?
- General decreased robusticity – more reliance on technology?
- Long body and limbs – adaptation to warm environment?
Earliest Homo sapiens
Current estimates for origin of AMH: 100 -250 kyr BP
Transitional forms between archaic and AMH
-300-120 kyr
- e.g. Omo II, Ethiopia (130kyr)
Early true AMH:
- 120-80 kyr
- e.g. Omo Kibish, Ethiopia (130kyr)
Omo I
- Long and curved parietals
- A short broad face and high forehead.
- Presence of a mental eminence.
- Modern appearing teeth in both size and shape.
- A cranial capacity of over 1400 cc (exact measurement is difficult).
- A low nuchal torus position.
Movement of early Homo
AMH in the Middle East from ~90Ky
-Skhul & Qafzeh (contemporary with Neanderthals)
AMH in Asia from ~40Ky
-Wadjak; Niah Cave, Borneo
AMH in Europe from ~35Ky
-appearing during an interstadial (warm period)
Earliest Homo in Europe
- The Upper Palaeolithic record of human remains is relatively sparse
- All anatomically modern, but very variable in robusticity and not very like modern Europeans
- Eastern european finds outnumber western
- eg 25-26k BP Predmosti
Multiregional
- AMH evolved over a wide geographical area over a prolonged period
- ‘Modernity’ evolved at different times in different places
- ‘Modern’ features were superimposed over local archaic features, producing regional continuity in morphology
- There is no particular significance to the origins of modern humans
- M H Wolpoff
Recent African Origin
- Modern human origins occur in a single place (Africa) relatively recently (c200kyr)
- Dispersal of populations and extinction of archaic forms is a primary mechanism
- Modern humans depart from general trends of archaic hominins
- Regional morphological trends postdate the evolution of modern features
- The origins of modern humans is a significant event
- Chris Stringer
Regional variation in homo
- Continuity of traits in particular geographic regions between archaic and modern (including extant) populations
- Australia + South East Asia - flat frontal bones, marked occipital tori, marked facial prognathism
- Eastern Asia - mid sagittal keel and parasagittal depression, flat face, flat zygomatic, shovel-shaped incisors
- Europe - large nasal bones, large faces
- Fossil evidence supports Multiregional hypotheses
Problems with Multiregional hypotheses
- Many of the proposed features are variable amongst both fossil and living populations
- Some are primitive features (supraorbital tori and occipital tori) – conserved in some populations & lost in others
- Some are regional adaptations (large noses, flat faces) – represent convergent evolution with populations adapting to local environments
- Some may not be truly homologous between archaic & modern populations (sagittal keeling)
Fossil evidence for recent African origins
- Oldest AMH fossils from Africa
- Fossils and archaeology suggest that AMH quickly replaced Neanderthals in Europe & Western Asia
- Body proportions of early modern Europeans suggest tropical/subtropical origin
- Far Eastern fossil record is problematic: poor descriptions, weak dating, variability
Possibility of Neanderthal/Sapien interbreeding?
- Possibility of some AMH-Neanderthal interbreeding as AMH move into shared territories
- Only c 2-3% of genome
- Still distinct enough to be seen as different species even if they don’t meet biological species criteria of no interbreeding
- Currat and Excoffier (2011)
- Spatial simulations
- Low levels of interbreeding (<2% success rate) compatible with ltd nuclear introgression and no mtDNA introgression
- Interbreeding only occurred in a narrow zone on the expansion front of the two populations
