Presentation on theme: "Paleoanthropology: Reconstructing Early Hominid Behavior and Ecology"— Presentation transcript:
1Paleoanthropology: Reconstructing Early Hominid Behavior and Ecology Chapter 10Paleoanthropology:Reconstructing Early Hominid Behavior and Ecology
2The Bipedal Adaptation Efficient bipedalism- only hominids.Advantages of bipedalism:Freed the hands for carrying objects and for making and using tools.In the bipedal stance, animals have a wider view of the surrounding countryside.Bipedal walking is an efficient means of covering long distances.
3Obligate BipedalismBipedalism as the only form of hominid terrestrial locomotion.Requires major anatomical changesOther forms of locomotion on the ground became impossible.
4Major Features of Hominid Bipedalism The foramen magnum (shown in red) is repositioned farther underneath the skull, so that the head is more or less balanced on the spine (and thus requires less robust neck muscles to hold the head upright).
5Major Features of Hominid Bipedalism The spine has two distinctive curves—a backward (thoracic) one and a forward (lumbar) one—that keep the trunk (and weight) centered above the pelvis.
6Major Features of Hominid Bipedalism The pelvis is shaped more in the form of a basin to support internal organs; moreover, the ossa coxae are shorter and broader, thus stabilizing weight transmission.
7Major Features of Hominid Bipedalism Lower limbs are elongated, as shown by the proportional lengths of various body segments.
8Major Features of Hominid Bipedalism The femur is angled inward, keeping the legs more directly under the body; modified knee anatomy also permits full extension of this joint.
9Major Features of Hominid Bipedalism The big toe is enlarged and brought in line with the other toes; in addition, a distinctive longitudinal arch forms, helping absorb shock and adding propulsive spring.
10Position of the Foramen Magnum (a) a human and (b) a chimpanzee.Note the more forward position in the human cranium.
11Paleoanthropology The study of early humans. Reconstruct the anatomy, behavior, and ecology of our ancestors:A diverse multidisciplinary pursuit.Physical SciencesBiological SciencesSocial SciencesGeologyPhysical anthropologyArchaeologyGeomorphologyEcologyEthnoarchaeologyGeophysicsPrimatologyCultural anthropologyChemistryPsychologyTaphonomy
12Dating MethodsPaleoanthropologists 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.
13Relative and Chronometric Dating Relative DatingChronometric DatingExamplesStratigraphyFluorine DatingK/ArRadiocarbon (14 C)Fission-trackMethodological basisProvides a sequence only; i.e., no estimates in actual number of yearsMost techniques* are radiometric; i.e., steady decay of radioactive isotope provides estimate in actual number of years
14Relative 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.
15Chronometric Dating Techniques Measure the rate of disintegration:Potassium/argon (k/Ar)1-5 million-year rangeHalf-life of 1.25 billion years.Dates rocks
16Chronometric Dating Techniques Carbon-14Less than 1, ,000 yearsHalf-life of 5,730 years
17Steps in Interpreting Homind Evolutionary Events Selecting and surveying sites.Excavating sites and recovering fossil hominids.Designating individual finds with specimen numbers for clear reference.Cleaning, preparing, studying, and describing fossils.Comparing with other fossil material.Comparing fossil variation with known ranges of variation in closely related groups of living primates and analyzing ancestral and derived characteristics.Assigning taxonomic names to fossil material.