Archaeology Topic 1 and 2
Survey and Fieldwork
(the systematic search for archaeological sites) - yields data on site size, distribution, number, form - also yields data on local ecological zones and geographic features
DATING METHODS
*BC (Before Christ) = BCE (Before the Common Era) *AD (Anno Domini) = CE (Common Era) *BP (before present - often used with radiocarbon dating) Dating is a primary objective of archaeology - nothing else is possible without it Direct Dating = analysis of the object itself Indirect Dating = analysis of material associated with a given object. Depends on context
Archaeology and History
- Both study the past - History is based on written documents; archaeology on material culture - History is limited to at most 5,000 years; less than 100 in some regions - History - limited primarily to literate societies - Written records tend to focus on the rich and powerful
GEOMAGNETISM
- Looks at large-scale reversals of Earth's north - south polarity - used only occasionally, to confirm other dating methods
OBSIDIAN HYDRATION
- Obsidian = volcanic glass - common stone tool material - When fractured - edge begins to absorb water (= "hydration") - hydration penetrates into the stone at a known rate - can be measured Limitations: - regionally specific - depends on temperature, moisture, etc. - each obsidian source is different
Archaeology and Science
- Science is the systematic pursuit of knowledge about natural phenomena. - Archaeology interacts with many different sciences: - Geology - e.g., understanding what types of stone were selected for stone tools - Biology - e.g., identification of bones of extinct species - Physics and Chemistry - e.g., radiocarbon dating - Astronomy - e.g., was Stonehenge aligned with the summer solstice? BUT (and a big but...): archaeology is a social science. - Since archaeology deals with human behaviour, it is often less predictable than the natural sciences - people are dynamic and complex, because of individual personality, culture, and motivations.
RADIOCARBON DATING
- Willard Libby 1949 - a radiometric dating method, based on radioactive decay of isotopes - (isotopes = different forms of an element with different "atomic weights", ie., different numbers of protons and neutrons in the nucleus) - some isotopes are stable, others are unstable - unstable isotopes gradually decay, changing into stable elements - can be used to date objects, if you know: 1) original amount of isotope 2) amount remaining at present 3) rate of radioactive decay - rate of decay is measured by a half-life = the time it takes for half of the isotope to decay
POTASSIUM-ARGON DATING (K40-Ar40)
- another form of radiometric dating - used to date volcanic rock, not artifacts or other human products - minimum age 5,000 years, no maximum age (half life 1,330,000,000 years) - useful in regions with lots of volcanism - when rock is heated, drives out all Argon, and then potassium decays to argon over time at known rate.
Historical Archaeology
- archaeology with aid of historic records. - documents do not give the complete picture, and only archaeology can fill the gaps e.g. - how did "commoners" live?
STRATIGRAPHY (relative)
- based on the sequential laying down of strata - 17th century - Law of Superposition: "where one layer overlies another, the lower layer was deposited first" - strata are created both by humans and natural processes - Potential Problem: Disturbance: 1) garbage pits 2) burrowing animals (rodents, dogs) 3) floods washing layers away, redeposition
Accelerator mass spectrometry (AMS) (Improved Radiocarbon Dating)
- conventional dating - measure beta emissions - requires about 5 gm pure carbon = 10 gm charcoal, 200 gm bone. - AMS - measures the amount of C14 directly - requires only tiny samples: 1) artifacts themselves can be dated 2) small or valuable objects can be dated 3) if organics are rare, single seeds, twigs, etc. can be dated
Screening (sifting)
- critically important to recover full range of material - pass soil through screen in order to find small artifacts and ecofacts - Flotation - special type of screening - materials lighter than water are collected from surface
ABSOLUTE DATING
- dated to a specific year either Before Present or according to a calendrical system
CALENDAR DATING
- e.g. dates on grave stones, monuments, written documents calendars Greeks - from date of first Olympics - 776 BCE Muhammad's departure from Mecca = 622 CE Egypt, China in terms of successive dynasties Limitations: 1) must be long, with no gaps - eg. dynasties need to list all kings 2) must be linked to a known date, or else it is relative
RELATIVE DATING
- earlier or later than something else - ordering things in a sequence - not as precise
Surface survey
- most common - walking - looking for surface artifacts - aerial survey - airplanes, helicopters, drones
Factors that affect the archaeological record
- not all behavior will leave material traces due to intervening cultural and natural processes, the archaeological record is not usually a direct reflection of past behavior Artifact - Any object made or modified by people. Ecofact - Natural object used or affected by people. Feature - Non-portable material remains resulting from human activity (e.g., a house, a fireplace, a midden). Archaeological site - A place where evidence of past human activity is preserved.
Site Evaluation
- once a site is found, you must determine size, type, layout - produce accurate maps - plot surface artifacts and ecofacts - subsurface testing
CONTEXT
- provenience and associations of an artifact, feature, or archaeological find in space and time - Provenience = three-dimensional location of an artifact or feature - Association = two or more items occurring together usually in same level, feature, etc. - e.g. artifacts associated with burial
Classical Archaeology
- specialized subdiscipline - classical civilizations of Greece and Rome from about 700 BCE - 500 CE. - allied with art history, history
DENDROCHRONOLOGY (= tree ring dating)
- temperate areas - trees dormant during winter - well-defined growth rings which vary by year in regular patterns - Today - many sequences - oak trees from southern Germany - 11,000 years - Sophisticated uses, e.g. sequences of construction and occupation of complex sites Limitations: - requires preservation - reuse of old wood, e.g. as beams (date is of cutting, not use) - need a regional chronology - complex and time-consuming - useful only outside of tropics
Subsurface techniques
- used to identify buried remains - simplest, most common = test pitting - using shovel - Non-invasive methods for subsurface detection: - Soil Resistivity - resistance to electrical current - Ground Penetrating Radar - bounces electromagnetic waves off of subsurface features
Frequency Seriation (relative)
-more precise means of determining an ordered sequence - based on the fact that any artifact type will be initially rare, then well-accepted, and then die out as it is replaced. - measuring changes in the proportional abundance (frequency) of artifacts limitations: the artifact types must occur over a large region, and must occur in significant frequencies
Excavation Strategy
1) Vertical Excavation: - stratigraphy, change through time - deep probes, generally used to construct chronologies 2) Horizontal Excavation: - spatial distributions at a specific time - single deposit or former living surface looks at relationships between artifacts, ecofacts, features, etc.
Limitations of all C14 dating:
1) contamination before sampling: carbon in groundwater, modern plant roots, etc. 2) contamination during sampling: cardboard labels, glue, mould, etc. 3) sample is older than context (e.g., old wood used to build house) 4) some materials contain ancient carbon (eg. sea mammal bone) 5) maximum date about 50,000 years
SERIATION = TYPOLOGICAL SEQUENCES (relative)
= artifact change over time - Technology and fashions change (eg. cars, clothes, music, etc.) - some artifacts change more quickly and regularly than others - eg. pottery; arrowhead types Stylistic Seriation: - most often pottery - types or styles - presence / absence
Archaeology and Anthropology
Anthropology = the study of humankind - a holistic discipline - archaeology adds a historical dimension, and comparative case studies - 4 subdisciplines: - Archaeology - Social-Cultural Anthropology - Linguistic Anthropology - Biological Anthropology
A final note...
Archaeological Excavation is Destructive! - only dig what is necessary to answer current questions - record, photograph, and draw everything.
How are sites found?
Chance or Accident: - e.g. cave paintings in Lascaux (schoolboy's dog), "Ice man" (found by hikers) Use of documentary sources - e.g. L'Anse aux Meadows viking site in Newfoundland Salvage archaeology: - determined by industrial or urban development plans or site destruction Archaeological survey: - Survey of regions. Allows reconstruction of settlement pattern = distribution of sites across the landscape
Excavation
Excavation is necessary to acquire detailed information - often, buried deposits are better preserved and less disturbed than surface deposits - only buried deposits allow archaeologist to infer association - buried deposits provide the best evidence for change in activity over time - the key = retaining exact 3-dimensional record of context
HOW DO ARTIFACTS ENTER THE ARCHAEOLOGICAL RECORD?
Four stages: 1) acquisition - either direct or through trade 2) manufacture - modification of raw materials 3) use - leaves traces on artifact; can also be interpreted from where the artifact is found 4) deposition - entry of the material into the archaeological record. **artifacts can enter the archaeological record at any point in this process.
WITH ALL DATING METHODS: DEMONSTRATION OF ASSOCIATION IS KEY
Generally - try to use at least two methods to confirm date e.g. stratigraphy + C14 method Every dating method has problems and limitations
GEOCHRONOLOGY (relative)
Horizontal stratigraphy: - in some areas, occupation moved horizontally in a predictable way. - e.g., series of beach ridges are formed as a waterbody recedes - eg. Cape Krusenstern, Alaska Limitations: A) Beach ridges must be formed in a regular fashion B) Activity must be confined to waterfront beach ridge
Processes that Transform the Archaeological Record
Natural Factors: - climate - temperature and humidity - extreme wet, dry, or cold preserves organics - biological factors - eg. decay, rodents, carnivores. - soil chemistry - can destroy (acid) or preserve (fossilize) - catastrophic events (volcanoes, earthquakes) Cultural Factors: - Large Scale Human Events (e.g., war) - Looting - encouraged by the antiquities market - Disturbance through industrial or agricultural development
what is archaeology?
is the study of material remains (physical objects) and their spatial relationships to interpret past human behaviour
The archaeological record
it is the sum of all physical evidence about the past that survives to the present (objects plus their context)
SECONDARY CONTEXT
location and association are ALTERED, so less information is available to the archaeologist
PRIMARY CONTEXT
undisturbed since deposition of artifacts by people who made and used them e.g., burials, living floors, houses, middens