Paleoanthropology: Reconstructing Early Hominid Behavior and Ecology 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 Biocultural 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.

Major Paleoanthropological Projects

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.

Flake and Core

Direct Percussion

Pressure Flaking

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.

Possible Factors Influencing the Evolution of Bipedalism 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

Possible Factors Influencing the Evolution of Bipedalism 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

Possible Factors Influencing the Evolution of Bipedalism 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