Paleoanthropology: Reconstructing Early Hominid Behavior and Ecology

1
Chapter 9

• Paleoanthropology Reconstructing Early Hominid
  Behavior and Ecology

2
Chapter Outline

• Definition of Hominid
• The Strategy of Paleoanthropology
• Paleoanthropology in ActionOlduvai Gorge
• Dating Methods
• Excavations at Olduvai
• Experimental Archaeology
• Reconstruction of Early Hominid Environments and
  Behavior

3
Definition of Hominid

• Characteristics significant in defining hominids
  
• Large brain size
• Tool making behavior
• Bipedal locomotion

4
Patterns of Evolution

• Mosaic evolution
• Evolutionary pattern in which physiological and
  behavioral systems evolve at different rates.
• Biocultural evolution
• Biology makes culture possible and developing
  culture further influences biological evolution.

5
Biocultural Evolution The Human Capacity for
Culture

• The earliest hominids of 7-5 m.y.a. did not
  regularly manufacture stone tools.
• Stone tools appear in the archaeological record
  about 2.5 m.y.a.
• The dynamics between neuronal reorganization,
  tool use, changing social organization, and
  communication form the core of biocultural
  evolution.

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Paleoanthropology

• Paleoanthropologists use the skills of several
  disciplines to reconstruct the anatomy, behavior,
  and ecology of our ancestors
• Geologists work with anthropologists to locate
  potential early hominid sites.
• Archeologists excavate the site and search for
  hominid traces.

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Dating Methods

• Paleoanthropologists use two types of dating
  methods to tell us the age of sites and fossils
• Relative dating determines only whether an object
  is older or younger than other objects.
• Chronometric (absolute) dating provides an
  estimate of age in years based on radioactive
  decay.

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Relative Dating Techniques

• Stratigrapy - based on the law of superposition,
  that a lower stratum (layer) is older than a
  higher stratum.
• Fluorine analysis applies to buried bones and
  groundwater seepage. Bones incorporate fluorine
  during fossilization.
• Biostratigraphy - related to changes in the
  dentition of animals.
• Paleomagnetism - based on the shifting of the
  geomagnetic pole.

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Chronometric Dating Techniques

• The age of an object can be determined by
  measuring the rate of disintegration
• Potassium/argon (k/Ar) dating involves the decay
  of potassium into argon gas. K/Ar has a half-life
  of 1.25 billion years.
• Carbon-14 is a radiometric method commonly used
  by archeologists. Carbon 14 has a half-life of
  5730 years.

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Major PaleoanthropologicalProjects
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Paleoanthropology in Action-Olduvai Gorge

• Yielded the greatest quantity of high-quality
  data on early hominid behavior.
• The earliest hominid site dates to about 1.85
  m.y.a., and is accompanied by the Oldowan tool
  industry.
• The most famous hominid fossil from Olduvai is
  the Zinjanthropus skull, discovered by Mary
  Leakey in 1959.

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Excavations at Olduvai

• Three broadly defined site types present at
  Olduvai.
• Butchering localities - one or a few large
  mammals associated with archaeological traces.
• Quarry localities - areas where hominids obtained
  stone and initially fashioned stone tools.
• Multipurpose localities (campsites) - where
  hominids carried out daily activities.

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Stone Tool (Lithic) Technology

• The most commonly preserved aspect of hominid
  cultural behavior.
• Initially, archaeologists thought the Oldowan
  industry consisted of deliberately fashioned
  cores and flakes.
• Richard Potts believes that only the flakes were
  being deliberately produced, and the core tools
  were merely byproducts of flake manufacture.

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Flake and Core
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Direct Percussion
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Pressure Flaking
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The Bipedal Adaptation

• Efficient bipedalism among primates is found only
  among hominids.
• All the major structural changes required for
  bipedalism are seen in early hominids from East
  and South Africa.
• Some researchers believe these early humans also
  spent considerable time in the trees.

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Possible Factors Influencing the Evolution of
Bipedalism
Factor Speculated Influence
Carrying objects Upright posture freed the arms to carry various objects (including offspring)
Hunting Carrying weapons made hunting more efficient long-distance walking may have been more energetically efficient
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Possible Factors Influencing the Evolution of
Bipedalism
Factor Speculated Influence
Seed and nut gathering Feeding on seeds and nuts occurred while standing upright
Cooling Vertical posture exposes less of the body to direct sun increased exposure to breezes
Visual surveillance Standing up provided better view of potential predators as well as other group members
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Possible Factors Influencing the Evolution of
Bipedalism
Factor Speculated Influence
Long-distance walking Covering long distances was more efficient for a biped than for a quadruped mechanical reconstructions show that bipedal walking is less energetically costly than quadrupedalism
Male provisioning Males carried back resources to dependent females and young