Archaeological Science and Theory

GIS/GPS

-GIS = Geographic Information System -GIS is a framework to gather, manage, and analyze spatial and non-spatial data. Most basically, GIS technology is used as computer cartography, to quickly and easily make virtual maps. More complicated, GIS technology also allows for spatial and statistical methods to be applied to analyze geographic and attribute (nonspatial data associated with geographic locations) data. Put another way, GIS refers to the use of layers of geographic data to both produce spatial analysis and also create maps. -GPS = Global Positioning System -GPS is a satellite-based navigation system, which can provide locational data anywhere on the planet, as long as there are at least four satellites in line of sight. Interesting fact, GPS is actually a subcategory of the larger term 'Global Navigation Satellite System' (GNSS); GPS is just the United State's version of a GNSS, but it has entered common parlance as a more general term. There are currently 33 satellites in the United State's GPS network

LIDAR

-Lidar, LiDAR, LIDAR = portmanteau of 'light' + 'radar' ; also 'Light Detection and Ranging' -Lidar is a remote sensing method that uses light in the form of a pulsed laser to measure ranges (variable distances) to the Earth. Most common is airborne Lidar, where you stick the device on an airplane or drone and fly it above a landscape. People also do terrestrial Lidar, where you stick the device on a tripod. Lidar is most useful in the creation of extremely accurate elevation maps (DEM = digital elevation map) over very large areas. Notable about Lidar is its ability to 'remove' tree cover and vegetation from its maps; this has been used to great effect by archaeologists in tropical or heavily forested areas. Lidar can do in an afternoon what used to take years of research on foot.

Radiocarbon Dating

50 kya theoretical limit but 40 kya the limit in practice, although more and more calibrations are refining this. 14C radiocarbon is made by radiation from the sun when 14N turns into 14CO2 and gets into the food cycle. 14C half life is 5730 years. The first radiocarbon dating method used "beta-decay" counters, needed 8g of carbon, took a long time to count the emissions. The result was a "conventional" radiocarbon date. Then the advent of Accelerated Mass Spectrometry (AMS) ca. 1977 allowed for counting the number of 14C atoms present in the sample and knowing the relative proportion of 12C, 13C, 14C. Radiocarbon dating measures the time since death of the organism. AMS requires a particle accelerator. The production of radiocarbon in the atmosphere is not steady, must be calibrated. AMS costs 1200/sample or 400/sample at the friend rate.

Uranium Series Dating

50-500 kya. 238U, 235U isotopes made during the earth's formation decay into other elements which decay further eventually leading to a stable isotope of lead. U-Th applicable to limestone (calcium rich) layers. U-Pb mostly used in geology on zircon (>1mya). U-Th isotopes not found in living humans; if it is present in a bone sample, all you can say is that the sample dates from before the resulting date (ie., when did the Uranium in the water uptake into the bone). Used to date cave art (El Castillo Cave, Spain, >37 kya) implying the art could have been made by Homo sapiens or neandertalensis. Also used to date the oldest known Homo sapiens sample in Morocco (100 kya).

Lipids

A biomolecule soluble in nonpolar solvents like fats, waxes, and resins. Lipids are a major focus of organic residue analysis as they are the least susceptible biomolecule to decay (nucelotides are the most susceptible). Animal fats and plant oils can be identified if stable isotopic composition of n-alkanoic acid biomarkers are determined. However, lipids analysis lacks taxonomic/tissue specificity and mixes different food products so shotgun proteomics can be used to identify individual proteins unique to particular cereals, pulses, dairy, and meat products.

Post-colonialism

A body of critical theory dealing with the effects of colonization on cultures and societies, focusing on the human consequences of the control and exploitation of colonized people and their lands, and derives from anticolonial thought from South Asia and Africa in the first half of the 20th century but now encompasses other regions like South and Latin America. [Pulling straight from wikipedia here, but,] Frantz Fanon, Edward Said, Spivak, Bhabha, Chakrabarti. Examples in archaeology, ML, Silliman, and authors in: Jane Lydon, & Uzma Z Rizvi. (2016). Handbook of Postcolonial Archaeology (Vol. 3, World Archaeological Congress research handbooks in archaeology). Walnut Creek: Taylor and Francis.

Post-processual archaeology

A historical moment in the 1980s and 1990s by people broadly critiquing processual archaeology by drawing on a host of bodies of theory. Broadly speaking, postprocessualists rejected a positivist view of science and the material/ideal opposition, considered data as theory-laden, interpretation as hermeneutic, the individual as agentive, and material culture as textual. The most strident anti-processual figures include Ian Hodder, Michael Shanks, Christopher Tilley (Contextual-try to determine thoughts and values in the past) but other strong critiques came from Feminist theory ( Meg Conkey, Joan Gero, Alison Wylie, Maria Franklin), Indigenous Studies (Geroge Nicholas, Sonya Atalay, Steven Silliman, Joe Watkins) and Postcolonial theory.

Wave of advance

A migration-driven model for the spread of agriculture into Europe (but since applied or tested in other areas of the world-see early models for the peopling of Tibet). In 1971, Ammerman and Cavalli-Sforza used radiocarbon dates from Neolithic sites to propose a "wave-of-advance" model where local population growth and migration produce demographic expansion in a traveling wave from the southeast to the northwest of Europe. The model argues that farmers expanded into Europe from West-Asia about 10,000 years ago, and replaced resident hunter-gatherers with little or no genetic admixture. The alternative "cultural" model proposes technologies were transmitted to the resident hunter-gatherers who changed their lifestyle and converted to farming.

Optimal Foraging Theory

A theory for developing models of human behavior (especially in regards to food procurement) based on neoclassical microeconomics (the "rational actor" and "all things being equal") and evolutionary theory (organisms adapt to their environment).

Processual archaeology

A turn to use post-world war II scientific method to explicate and explain the total range of physical/cultural similarities and differences of the entire spatio-temporal span of human existence. The focus is on process, systems, and a broadly positivist approach. "Explanation" is the demonstration of repeated presence of variables with a system and a measurement of the variability within the system. For Binford, the system is the extrasomatic (non-biological) means of adaptation (survival in the changing environment). In simpler words, processual archaeology is engaged with explaining culture change (as compared to documenting culture history).

Chaîne opératoire

Although frequently translated as 'operational chain', the English term does not capture the depth of meaning. Most surficially, chaîne opératoire refers to the technological sequence of processes required to make something, most frequently lithic tools. To make a Mousterian side scraper, you have to strike stone at a certain angle, reposition it in your hand, strike at another angle, and so on. More deeply, chaîne opératoire describes the internal logic implied by the technological sequence of tool creation processes; tool creation is a social and cognitive product, not just material. This concept is most closely aligned with French archaeologist Leroi-Gourhan.

Stable Isotope

An elemental isotope that does not undergo spontaneous radioactive decay; it is the result of variation in the number of neutrons in an atom's nucleus. These ratios of the different isotopes within an organism reflect the broader ratios found in environments and diets.

Dual Inheritance Theory

An evolutionary framed theory promoted by Richerson and Boyd in 1978 in order to explain how much of human behavior is not determined by genetic inheritance but is rather learned and "escaped the control of natural selection acting on genes." Their "dual-inheritance" models proposes a genotype inherited in the traditional Darwinian manner and a second "culture-type" related to, but separate from, whatever gene accounts for the capacity for culture. This "culture-type" is the message an organism inherits from other individuals of the same species. The Dual-Inheritance model becomes foundational for hunter-gatherer research using HBE or other model-based methods.

Dendrochronological calibration & Radiocarbon calibration curve

Conventional radiocarbon date takes into account Libby's wrong half life, the analytical error of the instrument, fractionation correction due to different photosynthesis methods, and assumes "present" date of 1950. The conventional date still needs to be calibrated to the variation in the rate of cosmic rays, De Cries effects that shift the amount of radiocarbon produced each year. This has been done by taking radiocarbon samples from tree ring records (whose ring is known to correspond with an absolute date). Beyond the tree ring limit, records taken from deep sea cores and other geological methods. Calibration should also take into account the marine reservoir effect, if site is close to the sea, and hemispheric effects.

Dental Calculus

Dental calculus is visible as a layered, mineralized accretion adhering primarily to the enamel crown and a small amount adhering to the tooth root. Dental calculus on archaeological teeth often has a "lipped" appearance, indicating where it once abutted and grew over the gingiva. Calculus is made up of calcium phosphate primarily in the form of hydroxyapatite, the same mineral that makes up the inorganic portion of bone, dentine, cementum, and enamel. Microbotanical remains like phytoliths and starch granules can be recovered from dental calculus. Biomolecules recovered from dental calculus can be used for ancient DNA and paleoproteomic analyses.

ESR dating

Electron spin resonance can be used on materials like tooth enamel or eggshell. Unlike TL, OSL, electrons are not released. Good for material >100 kya. Measures the time since burial or site formation. Uses microwave radiation to make electrons flip rotation and measures the amount of energy required to make this flip. Needs a 5g sample (a lot), need to know local dose rate, high error rate.

TL Dating

Heat releases energy (measured as light) which is absorbed in crystal defects. The resulting date reflects the time since the sample was last heated. Material dated is burned stone. Works for <100 kya

Organic Residue Analysis

ORA is the umbrella term for identifying archaeological biomarkers (substances occurring in organic residues that provide information about human activity in the past) from artifacts (pottery, human/animal remains, plant remains, dyes/pigments, soils/sediments, resins/bitumens, glass/metal containers, stone objects, well-preserved organics). It relies on spectroscopic methods like Nuclear Magnetic Resonance, which could be used to fingerprint plant resins and geographic origins, but has been revolutionized by gas chromatography-mass spectrometry where we can now identify chemical compound classes. The first archaeological use of GC-MS was to ID the chemical composition of bog butters in 1970. Like most arch sci methods, the questions being asked of the method need to be really thought out and often times rely on deductive reasoning as in the case of concluding the presence of theobromine in Preclassic Maya spouted vessels is related to cacao (theobromine is in a number of plants but only in cacao in Mesoamerica).

OSL Dating

Optically stimulated luminescence is the measurement of low energy electron displacement. The luminescence signal is a blue violet light. Exposure to sunlight resets the clock. Material dated is non burned stone; cannot be used on bone. Must know local dose rate. High error rate.

C3/C4 Plants

Plants that photosynthesize via the C3 pathway include rice, wheat, soybeans and barley (95% of plant biomass). Plants that photosynthesize via the C4 pathway include maize, sugar cane, sorghum, millets, amaranths, and certain Brassicaceae.

Paleofeces

The more specifically human version of the term 'coprolite' (this can refer to animal feces as well). Paleofeces can be studied to determine the diet and health of the people who produced them through the analysis of seeds, small bones, parasite eggs, lipids, and ancient DNA. Paleofeces tends to preserve the above very well due to the 'Maillard reaction', where a chemical reaction creates a casing of sugar around the feces that protects the stuff inside (eww lol). To extract the information inside, researchers typically need to freeze the feces and grind it up into a power (ewwwww lol). Ahhh this is gross.

Neutron Activation Analysis

This is a method for determining the elemental composition of a sample like obsidian. Certain rare earth elements became highly radioactive after exposure to a source of neutrons. When a sample is bombarded with neutrons, the neutrons collide with atoms in the sample forming an excited compound. Almost immediately, the excited compound beings radioactive decay at a rate dependent on the unique half-life of the radioactive nucleus. After a pre-determined decay period, the detector measures either the emitted particles or gamma rays.

Micromorphology

This is the microscopic study of soils and sediments. In archaeology, this typically involves the analysis of buried soils, where researchers gather thin sections of archaeological contexts that they look at under a microscope. This type of research can be used to better understand site formation process or behaviors in the past, by identifying microscopic changes in soil formation or deposition of tiny seeds, charcoal flakes, or bone fragments.

Carbon Isotopes

Used to determine diet. 13C:12C, δ13C. Stable carbon isotope studies can be used to explore how much of the individual's diet was made up of C3 or C4 photosynthesizing plants. Samples are taken from bone collagen and tooth enamel, which is resistant to carbonate defects where carbonates in water are taken into the bone. C3 and C4 plants discriminate against the heavier 13C isotope at different rates. The fractionation rate is also affected by temperature/latitude, "canopy" effect, water, and nutrient availability. Further fractionation occurs as the plants become food for herbivores and omnivores and ultimately carnivores. The type of tissue sampled can also affect the results. A lot of controlled experiments are necessary to build the background reference data (and are necessarily modern).

Nitrogen Isotopes

Used to determine diet. 14N, 15N. There are a lot of different environmental factors that can affect the δ15N in an organism's bones so these environmental factors must be known in order to successfully interpret the δ15N results. When this is done, δ15N can tell you about trophic level of the sample and how much is marine-sourced. Plotting δ15N (y-axis) against δ13C (x-axis) can show the dietary contribution of different foods to different samples (were all individuals, human or animal, eating a homogenous diet from the same trophic level?).

∂18O

Used to determine mobility and trade. 18O:16O, ∂18O. The ratio of Oxygen isotopes reflects the temperature of a location and in archaeology is often used to explore the source of a raw material or where an animal/human was born (it is also used to provide information on changes in global climate). When tested on carbonate sources like marine shells, carbonate rocks, or chert, the ratio reflects isotopic composition of the ocean at the time of the carbonate formation. When tested on terrestrial organism, isotope values depend on the value in the water consumed and lost from tissues and the way animals take in oxygen. Like Strontium, sequential samples can be taken to explore seasonal migrations or year-round sedentism. 3 main isotopes. Fractionation uptake into the body is affected by temperature, humidity, precipitation, body metabolism.

Strontium

Used to determine mobility and trade. Taken up into the body through geology (δ87Sr from the formation of the earth, the product of 87Rb, 49 billion year half life) and groundwater (rocks with strontium erode into watersheds). Sequential sampling of dentine layers from large mammals or from teeth that erupt at known ages can provide information on seasonal mobility or mobility in an individual's youth. The results of strontium isotope tests can exclude a locality but can almost never positively identify an origin as many places have the same ratio signature. Strontium substitutes for Calcium in skeletal tissues in a small, but measurable, amount. No effective isotopic fractionation. Limits are that Sr isotopes are not useful for recent (<10kya) marine shell because ocean Sr values don't change; cuisine and nonlocal watersources change the Sr levels from local water level (nixtamalization). Sr isotope ratio measured using TIMS or MS-ICP-MS.

aDNA

aDNA refers to preserved deoxyribonucleic acid and genetic information contained within recovered from archaeological samples (human or animal). Until recently, PCR techniques copied and amplified targeted sections of aDNA but were limited by the decomposition pattern of DNA. High Throughput Sequencing addresses this problem and has led to a boom in aDNA studies. aDNA studies of humans address questions of kinship, population movement, the occurrence of disease, gender distributions, and evolutionary lineage. aDNA studies of non-human animals can be used to question how certain animals came to be associated with humans/human consumption.

mtDNA

mtDNA is the DNA located within the mitochondria, inherited exclusively from the mother. mtDNA evolves faster than nuclear genetic markers and so has been used as a "genetic clock" to estimate the dating of evolutionary divergences. It can also be used to explore maternal lineages. (The Y-chromosome can similarly be used to explore paternal lineage).