Chapter 7

Homo erectus

Nariokotome

1984 the bones of an 11 ½ year old boy were found under a tree along a dry stream channel west of Lake Turkana

Nariokotome

Most complete skeleton of an early hominin ever found.

Died 1.6 million years ago Know that Nariokotome was an adolescent boy

due to: Shape of the pelvis Eruption pattern of his teeth Unfused condition of growth plates of his

long bones

Surprising characteristics: Modern in stature Pronounced areas of muscle

attachment on his long bones

Very thin with narrow hips, and long arms & legs for his height

Bergmann’s & Allen’s Laws for Mammalian Body Proportions

Endocranial volume was 880cc., as an adult it would have had a capacity of 910 cc.

EQ of 3.3 vs. 3.1 for Homo habilis Expanded right frontal and parietal lobes Expanded left occipital lobes Lower left frontal lobes, assigned to Broca’s

area in modern humans, is larger than the corresponding region of the right.

* Language abilities???

Altriciality: The young are born immature and helpless in condition so as to require care for some time

Second Altriciality: Newborns have rapidly developing brains in the 1st year of life

Homo erectus sensu lato

Homo erectus: defined on the basis of Asian fossils

Homo ergaster: African fossils Geographic distribution distinguishes

Homo erectus from earlier hominins

Homo erectus sensu lato

Homo erectus sensu lato lived in: Africa Southern Europe South Asia East Asia Southeast Asia

After rapid expansion Homo erectus entered a period of relative stasis

Mode 2 Technology

1.5 million years ago a new technology emergedBiface

First tools that existed in the minds of their makers as tools

Mode 2 Technology

Other Mode 2 Technology

Mode 2 sites are most often situated in sand or gravel deposited by streams

They are also situated at higher elevations in different geographic settings

Handedness

Right hand preference Bipedalism allows hands & arms to

gesture Gestures + vocalizations = language

Fire

Homo erectus may have used fire WarmthScaring away predatorsCooking foodSocial opportunitiesCommunal attention

The Homo erectus Adaptive Niche

Grade shift in cognition

The Homo erectus Adaptive Niche

What we know about Homo erectus: Larger than earlier hominins Reduced sexual dimorphism Had a larger brain, absolutely, than earlier Homo & a

slightly larger EQ Had smaller teeth and face Had a body build adapted for efficient cooling Lived in a wider variety of habitats Had dispersed rapidly to many tropical and

subtropical regions of the Old World Made & used tools of much greater complexity

The Homo erectus Adaptive Niche

Reasonable inferences… Diets contained more high quality foods Home range of groups were up to 10x larger than

those of other apes The energy budgets of males & females changed

• “grandmother’s hypothesis” vs. male provisioned females

Change in life history patterns Encountered cognitive challenges

The Weed Hypothesis

Homo erectus was adept at invading disrupted environments and new locales

Rapid colonization an essential component of the Homo erectus niche

Homo erectus Cognition

More sophisticated spatial cognition Mental templates

Selective Advantages

Larger territory and more unpredictable food sourceLarge scale spatial thinking selection

Social lifeShape and spatial information

coordination selection

Bifaces & Sexual Selection

Standardized None found at butchery sites Few signs of heavy use Sites found with hundreds, but little

else Improvements in appearance, but not

in usefulness

Developments In Skill

Expansion in areas of the motor cortex

Arm & shoulder anatomy selection

Memory Systems

Procedural memoryChaîne opératoire more complex

manufacturing sequence Working memory

2 main subsystems

Language

Symbols + grammar = language Increased length & complexity of

sequential motor action could account for the expansion of the left inferior premotor cortex

Grammar like rules or linguistic instruction needed for creating handaxes???

Memory Systems

Less powerful processor?Expansion of ST memory system may

have allowed the processing of sounds, transmission of more elaborate meanings, and eventually participation in syntactic processes

Memory Systems

The visuospatial sketchpad & central executive performance correlate stronglyin isolation the VSSP would operate in

a pre-attentive, implicit fashion

Memory Systems

Increased LT capacity, especially the capacity for procedural memory and expertise