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Chapter 9. Paleoanthropology: Reconstructing Early Hominid Behavior and Ecology. Chapter Outline. Definition of Hominid The Strategy of Paleoanthropology Paleoanthropology in Action—Olduvai Gorge Dating Methods Excavations at Olduvai Experimental Archaeology
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Chapter 9 Paleoanthropology: Reconstructing Early Hominid Behavior and Ecology
Chapter Outline • Definition of Hominid • The Strategy of Paleoanthropology • Paleoanthropology in Action—Olduvai Gorge • Dating Methods • Excavations at Olduvai • Experimental Archaeology • Reconstruction of Early Hominid Environments and Behavior
Definition of Hominid • Characteristics significant in defining hominids: • Large brain size • Tool making behavior • Bipedal locomotion
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
