Chapter 2 Notes Methods of Studying the Human Past pp

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1 Chapter 2 Notes Methods of Studying the Human Past pp Objectives: What are archaeological sites and fossil localities and how are they found? How are sites and localities investigated? How are archaeological or fossil remains dated? Archeologists study things left behind by people tools, trash, traces of shelters Aim is to reconstruct societies that no longer exist Attempt to explain human behavior Physical anthropologists are interested in human remains Paleoanthropologists - study fossils to find evidence for human evolution I. Methods of Data Recovery (32-36) Artifacts: any object fashioned or altered by humans Ex. Flint chip, basket, axe, pipe, house or wall ruins Product of human behavior The way they were left in the ground is very important Context tells if objects are contemporaries or which are older/younger Archaeologists work with artifacts Paleoanthropologists work with human or other primate fossils A. Nature of Fossils fossil: any trace or impression of an organism of past geologic time that has been preserved in the earth s crust. Involves the hard parts of an organism: bones, teeth, shells, horns and woody tissues of plants Soft parts rarely fossilized Casts of footprints and bodies/parts found Number of ways organism/part can be preserved: 1. frozen whole 2. enclosed in fossil resin eg. Amber 3. bottoms of lakes and sea basins septic 4. tarpits, peat, oil or asphalt bogs unaltered fossils: entire organism preserved unaltered fossils make up only 1 percent altered fossils: remains of plants/animals that have been altered eg. Replacement of organic material by calcium carbonate or silica altered fossils scattered teeth, bone fragments etc. fossilization 1. organisms die 2. deposited in earth 3. covered by sediments and silt or sand 4. materials hardened 5. form protective shell 6. internal cavities of bones /teeth filled in with mineral deposits

2 II. 7. walls of bone decay 8. replaced by calcium carbonate or silica most likely to happen among marine animals protected at water bottoms caves excellent for fossilization -water containing minerals drip from ceiling forests poor for preservation grassy plains or savannas provide records esp. where volcanic eruptions or lake/stream sediment cover them Sites and Fossil Localities Sites: places containing archaeological remains Difficult to define boundaries of a site Examples of sites: 1. hunting campsites-hunters wait for game to pass 2. kill sites- game was killed and butchered 3. village sites- domestic activities took place 4. cemeteries- dead/belongings were buried fossil localities in paleoanthropology, a place where fossils are found A. Site and Locality Identification first fob of archaeologist is finding sites to investigate revealed by the presence of artifacts survey region and plot sites to excavate aerial photographs/satellite imagery soil marks: stains that show up on the surface of recently plowed fields sometimes presence of chalky soil is important sites spotted by kind o f vegetation they grow sites exposed by nature- soil erosion, droughts, glacial melting human activity can expose- plowing, stone quarrying etc. projects held up to identify and protect archaeological remains archaeological sites may be found just about anywhere fossil localities found only where conditions are right for fossilization discovery of artifacts may lead to discovery of fossil sites B. Site and Locality Excavation why am I digging? consider resources carefully planned needs to help understand cultural and evolutionary processes 1. Archaeological Excavation Land is cleared Excavation sites plotted Grid system: divided into squares and each is numbered and marked with stakes Datum point: starting point Each square is carefully dug Trowels used to scrape the soil Screens used to sift loose soils

3 Flotation: immersion of soil samples in water to separate heavy from light Stratified: layered; remains one on top of another Each square dug straight Walls between squares often left to mark grid 2. Excavation of Fossils Like archaeological excavation with some differences Fossil must be related to temporal place within the rock Temporal :of or relating to the sequence of time or to a particular time Paleoanthropological expeditions are usually made up of a team of experts in various fields Requires great skill and caution Tools include: - pickaxes, enamel coating, burlap for bandages and plaster of paris, brushes, dental picks. Bones covered with shellac and tissue paper to protect Fossil and matrix (earth immediately surrounding fossil) cut out of earth More shellac is applied to entire block Bones covered with burlap bandages dipped in plaster of paris Entire block is enclosed in plaster an burlap bandages splinted with tree branches Allowed to dry overnight Make a map of terrain an pinpoints the find on geological maps to aid future investigations 3. State of Preservation of archaeological and fossil evidence Inorganic materials more resistant to decay stone tools Preservation affected by climate Dryness of caves contribute Human feces source of information on: Prehistoric foods, how prepared, time of year Rain and humidity destroy woodwork, textiles, basketry Impressions sometimes preserved in plaster Depictions in stone carvings and pottery figurines III. Sorting Out the Evidence If records are not kept the value of archaeological materials in destroyed All digging is destructive Archaeologist s responsibility to record site Photographs and scale drawings made Materials processed in lab Block is cut open Tools for removal - hammer, chisel, dental drills, rotary grinders, pneumatic chisels, awls, needles. - Chemicals, hydrochloric and hydrofluoric acid Three hours of lab work for every hour of field work Artifacts cleaned and cataloged

4 Tedious and time consuming Determine function from traces of manufacture and wear Technology- the knowledge people employ to make and use objects Analysis of skeletal material provides insights into peoples diets Wear patterns on teeth People who eat more plants that meat will have a higher ratio of strontium to calcium in their bones Recent protests from relatives 1. Dating the Past Relative dating consists of finding out if an event or object is younger or older than another Absolute or chronometric dating- dates based on solar years 2. Methods of relative dating Stratigraphy- most reliable method of relative dating by means of strata Based on the simple principle that the oldest layer or stratum was first deposited and the newest layer was deposited last Lowest stratum contains the oldest artifacts We can find relative age compared to other artifacts Fluorine test amount of fluorine deposited in bones in proportional to their age Oldest bones contain the greatest amount of fluorine Problem- rate of fluorine formation in not constant, but varies from region to region Palynology involves study of pollen grains Kind of pollen found depends on kind of vegetation that existed at the time stratum was deposited Another kind depends on paleontology Sites with bones of extinct animals are older 3. Methods of Chronometric Dating Radiocarbon analysis a technique for chronometric dating based on measuring the amount of radioactive carbon left in organic materials Can measure up to 70,000 years Any radiocarbon date has a + attached to it Dendrochronology dating based on tree rings Applicable only to wooden objects Potassium-argon analysis based on a technique similar to that of radiocarbon analysis Following intense heating, potassium decays Measure potassium relative to argon Useful when studying volcanic debris Amino acid racemization (ra-"se-m&-'za-sh&n) Bridges a time gap between the effective ranges of the radiocarbon and potassium argon methods Based on the fact that amino acids change or racemize after death Problem- in the soil amino acids can be leached out introducing a source of error

5 Electron spin resonance measures the trapped electron population in bone or shell