Over the past few years, technological advances in laboratory analysis promise new pathways to learning many things about the past. Breakthroughs in DNA studies, in stable isotope analysis, and in remote sensing are but a few of the most recent methodologies readily embraced by the archaeological community.
DNA and Molecular Studies
Molecular archaeology is the application of molecular chemistry to archaeological objects or investigations.
An outgrowth of the bioarchaeology of the 1970s, the study of molecules has included the examination of lipids and other organic deposits inside pottery vessels and other objects, blood residue analysis, and opal phytoliths, as well as the study of DNA, the main building block of life.
The first attempts to identify intact fragments of truly ancient DNA appeared on the surface to be possible, and these tests became quite well known, including that of the insects trapped in amber used by Michael Crichton’s Jurassic Park. Unfortunately, these materials proved unworkable, as ancient DNA is easily contaminated and decays within a maximum of 50 000-100 000 years.
Although DNA does not survive longer than 100 000 years, the process of evolution can be used to discern more distant events by examining the molecular chains of modern DNA. Human, animal, and plant evolution occurs at extremely variable rates: diseases evolve faster than we can invent medications for them, while certain species of brachiopods have remained essentially unchanged for millennia. But at the molecular level, undetected morphologically, evolution occurs at a fairly fixed rate. An examination of DNA strands of modern-day beings can be used to determine the length of time since the last change.
Important studies incorporating DNA include much new information about human evolution, including the recognition of the Mitochondrial Eve, and the relationship of Neanderthal to Homo sapiens. Other studies involving molecular DNA have included the search for location of the originating plants of the world’s first domesticated crops, including einkorn and emmer wheat, maize and rice. These studies also have identified elements of the process of domestication, how closely related strands of the current crops are and how many times and when the plants were domesticated. Animal domestications have also been examined using DNA, including searches for the original domestication processes of dogs, horses, goats, and camelids (see DNA: Ancient).
Bone Chemistry and Stable Isotopes
Developed in the late 1970s by South African researcher Nikolaas van der Merwe and colleagues, the use of stable isotope research to investigate ecological processes in once-living tissue has mushroomed in the past decade. Stable isotope analysis measures the ratios of different forms of chemicals to identify the progress of ecological processes and interpret the processes, building a history of the living plant or animal. Chemicals frequently used in isotope analysis include carbon, nitrogen, hydrogen, oxygen, strontium, lead, and sulfur. Stable isotopes have been investigated in traces of organic residues found inside pots and on the edges of stone tools, and in animal bone, tooth enamel, and hair. Identified processes include dietary components, including the relative use of marine fauna such as seals, fish, and shellfish, domesticated plants such as maize and millet, cattle dairying, and age of weaning. Other studies have used stable isotopes to identify the geographic origin of plants, animals, and humans. Studies have examined nearly every time period including hominins, from Homo habilis and the Australopithecines to modern days (see Stable Isotope Analysis).
Remote Sensing
Geophysical prospection, also called remote sensing, is any of the several methods of seeing what is beneath the surface of the ground, without actually disturbing the ground. Aerial photography of archaeological sites has been used since the first decade of the twentieth century. The first extensive aerial remote sensing project was carried out in the 1920s when French geographer Pierre Paris took aerial photographs of Oc Eo and Angkor Borei in the Mekong Delta of Cambodia and Vietnam, revealing an intricate network of canals in the floodplain. Since that time, in addition to aerial photographs and satellite photos, a huge range of technology-assisted methods have been used to search for crop marks, to identify buried structures, or to map chemical or electrical variances within soils.
The use of aerial photographs and topographic maps has become a standard background research step on many if not most archaeological studies; these are today supplemented by satellite photography in most places in the world. Ground-penetrating radar and magnetometer surveys are used in many different venues as part of an excavation strategy to reduce costs, minimize damage, or amplify subsurface testing methodologies.
Satellite imagery came of age as a result of the release of images produced by NASA’s Jet Propulsion Laboratory and LANDSAT in the 1980s. Today, five satellites regularly produce images of the Earth for NASA. The application of GIS and its vast mapping capabilities have come close to revolutionizing the field of archaeology, allowing the projection of accurately scaled maps over large distances. The first extensive projects to use large-scale mapping are now over 30 years old - Rene Millon’s Teotihuacan Mapping Project of the mid-1960s and Carole Crumley’s Burgundy landscape project of the early 1970s. Today, fairly high resolution satellite imagery is easily accessible to researchers via such tools as Google Earth, including large land surveys.
Several newer methodologies have become available for use on archaeological sites, many developed in other disciplines and adopted for use in archaeology. Electrical resistivity tomography (ERT) is an outgrowth of medical diagnostic techniques such as magnetic resonance imaging (MRI), which was adopted by geophysicists to collect extensive electric current and electric potential data sets in multiple dimensions. ERT has been used successfully in several projects, including identifying structures and voids beneath the Temple of Apollo in Hierapolis. Geophysical diffraction tomography (GDT) involves burying a set of microphones in a grid across a site and firing 8 caliber shotgun shells at the earth, then using the soundwaves to identify buried masses. Lidar uses laser-driven pulses of light and multispectral cameras to scan and process digital information about a landscape. Used originally to map environments, lidar has been of demonstrable use in archaeological survey and mapping of monuments. Enhanced satellite imagery from DigitalGlobe’s QuickBird satellite contains both multispectral and panchromatic imagery which has enabled archaeologists to map crop marks with more precision (see Remote Sensing Approaches: Aerial; Geophysical).
Computer-assisted Imaging
Akin to remote sensing are the advances in imaging. Like remote sensing, these techniques use methods developed from the medical and geographic fields of endeavor; but they are focused on enhancing artifacts rather than landscapes; since these objects are smaller they are more likely to use traditional methods, such as computer tomography (CT) scanning. CT scanning builds a three-dimensional image of an object from a series of two-dimensional X-rays established in a radial pattern. CT has been used to examine mummies and heavily encrusted artifacts prior to, or instead of, invasive procedures.
Some initial tests have used geo-referencing of aerial photographs to map artifacts and features at the site and excavation unit level; combining these data with quantitative analysis has allowed some researchers to examine patterning of artifacts. Digital images of such fragile objects as rock art and ancient documents allow researchers to enhance images without endangering the objects themselves, such as the recent work on the Archimedes manuscript.
Three-dimensional virtual reconstructions of ancient buildings have been undertaken as object studies, both to preserve fragile remnants, to consider different possible reconstructions, and to educate the public about what structures looked like in the past. Still a fairly expensive project, three-dimensional reconstructions have been successful in reconstructing buildings in Egypt and the American Southwest.
World History
