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Chapter 7 Homo erectus

Chapter 7 Homo erectus

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Chapter 7 Homo erectus

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  1. Chapter 7Homo erectus

  2. 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

  3. 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

  4. 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

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

  6. 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???

  7. 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

  8. Homo erectus sensu lato • Homoerectus: defined on the basis of Asian fossils • Homoergaster: African fossils • Geographic distribution distinguishes Homo erectus from earlier hominins

  9. 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

  10. Mode 2 Technology • 1.5 million years ago a new technology emerged • Biface • First tools that existed in the minds of their makers as tools

  11. Mode 2 Technology

  12. 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

  13. Handedness • Right hand preference • Bipedalism allows hands & arms to gesture • Gestures + vocalizations = language

  14. Fire • Homo erectus may have used fire • Warmth • Scaring away predators • Cooking food • Social opportunities • Communal attention

  15. The Homo erectus Adaptive Niche • Grade shift in cognition

  16. 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

  17. 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

  18. The Weed Hypothesis • Homo erectus was adept at invading disrupted environments and new locales • Rapid colonization an essential component of the Homo erectus niche

  19. Homo erectus Cognition • More sophisticated spatial cognition • Mental templates

  20. Selective Advantages • Larger territory and more unpredictable food source • Large scale spatial thinking selection • Social life • Shape and spatial information coordination selection

  21. 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

  22. Developments In Skill • Expansion in areas of the motor cortex • Arm & shoulder anatomy selection

  23. Memory Systems • Procedural memory • Chaîne opératoire more complex manufacturing sequence • Working memory • 2 main subsystems

  24. 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???

  25. 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

  26. Memory Systems • The visuospatial sketchpad & central executive performance correlate strongly • in isolation the VSSP would operate in a pre-attentive, implicit fashion

  27. Memory Systems • Increased LT capacity, especially the capacity for procedural memory and expertise