HE - evolution + diversity in genus Homo

Sagittal keel (bump on skull)
Large face
Supraorbital torus (lump) - brow ridge
Occipital torus
Flat forehead

2003
Homo erectus may be one single, widely dispersed, long lived, polytypic taxon
Lots of variation within a single species (Homo erectus)

Lumping
Splitting

Method of categorising taxonomic groups
Lumps all samples into a single, highly variable taxon
Accept larger range of intraspecific variation within hominins

Method of categorising taxonomic groups
Splitting large, varriable groups into smaller chunks
Expect less variation and larger degree of morphological overlap

High quality diet:
- Meat consumption (increased carnivory)
- Potential aquatic resources
Evidence of butchery:
- Defleshing
- Disarticulation
- Marrow extraction
Smaller jaws and teeth
Cut marks more common

Name given according to the lumping method to all potential Homo erectus

Name given to potential Homo erectus specimens in East Asia
More derived - has keels (ridge) and tori (bony ridge)

Name given to the potential Homo erectus specimens in Africa and Georgia
More primitve - lacks keels and tori

Oldowan
Acheulian

Older than Acheulian tools
Chopping tools, flakes
Quartz, quartzite, basalt
Chipped in 2 direction

Newer than Oldowan tools
More sophisticated
Hand axes
Flint, basalt
Use of hammers, symmetry of both sides

Increased locomotor efficiency
Can travel further for food
Allowed expansion out of Africa

Fast growth
Absence of human-like growth spurt

Rightmire 2015
Found in UK, South Africa, Southeast Asia
Globally dispersed
Homo antecessor
Homo heidelbergensis
Homo longi
Homo bodensis

Multiregional evolution
Out of Africa
Assimilation

Regional adaptations
Gene flow
Continuity

Replacement

Combination of continuity and replacement
Interbreeding

Small islands and caves
Eg. Indonesia

Homo erectus after it dispersed to small islands - led to insular dwarfism

Height: 1m
Brain: 380 - 430cc
Made tools (cut marks in animal bones)
Insular dwarfism
Dward descendent of H. erectus

When large animals are stuck on small islands, they evolve to have a naturally smaller size
Not enough food available to sustain large-bodied organisms
Seen in elephants, hippos etc.

Mix of Homo sapiens-like and primitive features

Derived craniodental morphology with primitive Australopithecus-like postcranium
- Long arms
- Strong curved fingers associated with climbing
- Human-like legs and feet
- Homo-like cranium
- Small brain
- Evidence of tool making (countered thinking about larger brain being required for toolmaking)
Ritual behaviour - bodies found deep within cave systems

Cave in SA

Island in Indonesia

Degree of overlap in populations' trait distributions expected to grow smaller over time as they go through speciation

Same morphological criteria employed across hominin fossil record
Morphology and progression of speciation are correlated (BUT speciation not always marked by morphological differentiation between daughter species)

Onset of African aridity
Expansion of open grasslands
Led to evolution of:
- Increased carnivory
- Brain enlargement
- Long-distnace mobility
- Prolonged life history

Large, linear bodies
Elongated legs
Large brain
Reduced sexual dimorphism
Increased carnivory
Unique life history traits
Tool making
Increased social cooperation

Not all of the adaptations evolved at the same time
Some evolved substantially earlier/later than previously understood

Long hind limbs

Dietary flexibility in unpredictable environments
Cooperative breeding
Flexibility in development allowed range expansion and reduced mortality risks

Existed well before origin of this genus
So cannot necessarily be used to distinguish between genera/species

Larger average body and brain sizes

Variation found in early African H. erectus and other early African Homo
- Derived H. erectus characters
- Some primitive characteristics
- Small brain size
Suggests early dispersal of the species

Homo evolved during fluctuating moisture and aridity, shifting resource regimes and spatial heterogeneity dominant features of East Africa
Climate and landscape variability highlights different sets of adaptive problems
More likely to survive if able to easily adapt to constantly changing and shifting environments

- Increase in average body and brain size
- Changing dental size
- Increased toolmaking and stone transport

Suggests dietary expansion, developmental plasticity, cognitive evolution and social investments

Shift towards incisal preparation and molar shearing
- Tough plant products
- Animal tissues

Oldowan tools provide technological basis for expansion into southern and northern Africa and western Asia

Increased nutritional sufficiency resulting from:
- Tool use
- Social cooperation
- Higher quality diet

Greater range of phenotypic adaptive flexibility in response to environmental change
In mammals: larger body size = larger home ranges

Larger brain size
Potential for diverse body sizes
Inferred dietary flexibility
Cooperation

Enabled H. erectus to attain level of niche construction and adaptive versatility that allowed it to outcompete others

H. erectus
Georgia and Java, Indonesia

Sparse records
H. erectus may not have been first or only hominin to disperse from Africa

Increased body and brain size
Reduced mortality risk
Increased nutritional sufficiency
Enhanced niche construction and ranging

Episodic
Likely to have involved many populations and back migrations

Periods of intensified moist-dry variability

Reproductive strategy in which most of the females of a social group do not breed regularly
Provide alloparental care to the offspring of breeding females instead