Paleoanthropology: Reconstructing Early Hominid Behavior and Ecology

 The earliest evidence of hominids dates to the end of the Miocene and includes dental and cranial pieces.

 Learned behavior  Non-body adaptations to the environment.  Identified among our closest ape relatives.

 A pattern of evolution in which the rates of evolution in one functional system vary from those in other systems.

Locomotion Modern Homo sapiens Bipedal: shortened pelvis; body size larger; legs longer; fingers and toes not as long Early hominidBipedal: shortened pelvis; differences from later hominids, smaller body size and long arms relative to legs; long fingers and toes; probably capable of considerable climbing Miocene, generalized hominoid Quadrupedal: long pelvis; some capable of considerable arm swinging, suspensory locomotion

Brain Modern Homo sapiens Greatly increased brain size—highly encephalized Early hominidLarger than Miocene forms, moderately encephalized; prior to 6 m.y.a., no more encephalized than chimpanzees Miocene, generalized hominoid Small compared to hominids, but large compared to other primates; a fair degree of encephalization

Dentition Modern Homo sapiens Small incisors; canines further reduced; molar tooth enamel caps thick Early hominidModerately large incisors; canines somewhat reduced; molar tooth enamel caps very thick Miocene, generalized hominoid Large front teeth (including canines); molar teeth variable, depending on species; some have thin enamel caps, others thick enamel caps

Toolmaking Behavior Modern Homo sapiens Stone tools found after 2.5 m.y.a.; increasing trend of cultural dependency apparent in later hominids Early hominidIn earliest stages unknown; no stone tool use prior to 2.5 m.y.a.; more oriented toward tool manufacture and use than chimpanzees Miocene, generalized hominoid Unknown—no stone tools; probably had capabilities similar to chimpanzees

 Paleoanthropology is the study of early humans.  This field uses many aspects of other disciplines Physical Sciences Biological Sciences Social Sciences Geology Physical anthropology Archaeology GeomorphologyEcologyEthnoarchaeology GeophysicsPrimatologyCultural anthropology ChemistryPsychology Taphonomy

 Artifacts  Objects or materials made or modified for use by hominids.  Taphonomy  The study of how bones and other materials came to be buried in the earth and preserved as fossils.  Context  The environmental setting where an archaeological trace is found.

 Zinjanthropus cranium, discovered by Mary Leakey at Olduvai Gorge in 1959.

 Paleoanthropologists use two types of dating methods to tell us the age of sites and fossils:  Relative dating  Chronometric (absolute) dating

 Stratigrapy  Fluorine analysis  Biostratigraphy  Paleomagnetism

 The age of an object can be determined by measuring the rate of disintegration:  Potassium/argon (k/Ar)  Carbon-14  Thermoluminiscence

 This site, more than 1 million years old, was located when a hominid ulna (arm bone) was found eroding out of the side of the gorge.

Grouped into categories: 1. “Butchering” localities 2. Quarry localities 3. Multipurpose localities

 A dense scatter of stone and some fossilized animal bone from a site at Olduvai, dated at approximately 1.6 mya.

 Arrows indicate implement edge.

 Environmental Determinsim  Stable Carbon Isotopes

FactorSpeculated Influence CarryingUpright posture freed the arms to carry various objects. HuntingSystematic hunting is now thought not to have been practiced until after the origin of bipedal hominids. Seed and nut gathering Feeding on seeds and nuts occurred while standing upright.

FactorSpeculated Influence Feeding from bushesUpright posture provided access to seeds, berries, etc., in lower branches; analogous to adaptation seen in some specialized antelope. Thermoregulation (cooling) Vertical posture exposes less of the body to direct sun; increased distance from ground facilitates cooling by increased exposure to breezes.

FactorSpeculated Influence Visual surveillance Standing up provided better view of surrounding countryside (view of potential predators as well as other group members). Long-distance walking Covering long distances was more efficient for a biped. Male Provisioning Males carried back resources to dependent females and young.

FactorSpeculated Influence CarryingUpright posture freed the arms to carry various objects. HuntingSystematic hunting is now thought not to have been practiced until after the origin of bipedal hominids. Seed and nut gathering Feeding on seeds and nuts occurred while standing upright.

 Efficient bipedalism as the primary form of locomotion is seen only in hominids.  Advantages of bipedalism:  Freed the hands  Wider view  Cover long distances efficiently

 Bipedalism as the only form of hominid terrestrial locomotion.