The Scope of Archaeological Geology. The History of Science in Archaeology

Physical scientists—geologists, chemists, physicists—have tried to solve archaeological problems longer than archaeology has existed as a recognized discipline. Few would argue today that scientists should stay away from archaeology and leave it, as it once was, reserved to the humanities. Nevertheless, the union of science and archaeology, although more and more a happy one, has on past occasions resulted in both minor and not-so-minor disasters. To avert disaster, the scientist must appreciate the problems and materials of the archaeologist, and the archaeologist should be knowledgeable about the virtues and pitfalls of scientific methodologies.

One of the earliest not-so-minor disasters that resulted from a scientist playing with unfamiliar historical materials occurred in 1818. In response to a plea from the king of Naples, the king of England sent Sir Humphrey Davy to help with the unrolling of papyrus scrolls. The scrolls had been discovered more than 60 years previously in a villa near Herculaneum. A local friar devised a complicated contraption with which he could separate the papyrus sheets, but extremely slowly. At the rate the scrolls were being unrolled, the king of Naples felt it would take several centuries to get the job done. Europe was clamoring to know the contents of the first classical library ever discovered and had also become impatient with the slow progress of the local Neapolitan talent.

Sir Humphrey arrived, complete with his portable lab and chemicals. He started work immediately on the scrolls, armed with all the knowledge of early 19th-century science (to which he had contributed a significant portion). Eleven scrolls were selected, and Davy's rapid chemical method was applied. All eleven were destroyed in the process before any attempt could be made to decipher the inscriptions. Whether he was deliberately sabotaged (an English interpretation) or was unlucky in the choice of scrolls submitted for the experiment will never be known. However, the incident serves as a great object lesson for teaching scientists proper humility in approaching archaeological problems.

Archaeologists are largely concerned with the esthetics and function of objects and with the cultural and demographic implications of settlements. Scientists are more interested in the nature of raw materials and their related technologies and in the siting and paleoenvironments of early settlements. The primary tool of the field archaeologist has been a shovel; the scientist could not function without a laboratory.

The History of Science in Archaeology. M. H. Klaproth, the great German chemist and discoverer of the element titanium, made one of the earliest contributions to archaeometry. In 1796 he published the results of chemical analyses of Greek and Roman coins, as well as of glass. In 1815 Humphrey Davy analyzed paint pigments that dated to the time of the Roman emperors. Close cooperation between the field archaeologist, Henry Layard and the scientist T. T. Philipps finally occurred during the excavations at Nineveh and Babylon. An appendix to the 1853 excavation reports included analyses of artifacts uncovered on the dig.

By the end of the 19th century, archaeology had developed its formal systematics, and excavations started to be carried out in an orderly fashion. Artifact hunting was abandoned, and many strategies from geology were adopted. Careful attention was paid to soil, sediments, and stratigraphic position; cooperation with scientists became more routine. Chemical and physical analyses of artifacts, pigments, and alloys began to appear, either in excavation reports or in scientific journals.

New discoveries made in physics at the end of the 19th century were applied to archaeological problems. In 1896 Roentgen, discoverer of x rays, noted their absorption by lead pigments in a painting by Durer and thought that x rays might be used to analyze pigments and help to detect fakes. Archaeological geophysics was born the same year when an Italian, Folgheraiter, measured magnetic moments in Etruscan pottery. Aerial photography from a tethered balloon was used successfully for archaeblogical prospecting in England by Beazely in 1919 to locate many Roman and pre-Roman structures.

Both archaeology and geology were handicapped through the first half of the 19th century by the universal acceptance of biblical stories to explain natural phenomena. For example, unconsolidated sediments lying over bedrock were classified as either diluvium (that is, deposited by the Noachian flood) or alluvium (post-flood). Human skeletal remains in sedimentary deposits were considered to be part of an earlier population that had been wiped out in the Noachian flood, named Homo diluvii testis (man who witnessed the flood) by the Swiss geologist Scheuchzer in 1726, or they were thought to be accidental intrusions or burials.

In the early 19th century, J.-C. Boucher de Perthes discovered worked flints and stone tools in diluvial gravels of the Glacial period in the Somme River Valley at Abbeville in France. The worked flints and extinct megafauna were found in situ in undisturbed gravel beds 5 m below the original surface. Clearly the human remains were the same age as the sedimentary deposits within which they were found and could be dated within the context of their enclosing sedimentary deposits. Archaeological remains could be analyzed by geological methodology; geological evidence was applicable to archaeological problems. The link between the two sciences was firmly forged with the establishment of the antiquity of humans.

Charles Lyell, one of the most important scientists of the last two centuries, visited the Abbeville site. He had already helped establish geology as a discipline with the publication of his Principles of Geology (1830-33). In 1863, after a visit to Abbeville, he published Geological Evidence of the Antiquity of Man, in which he used a geological context to document the known remains and artifacts of early humans. This book united geology and archaeology as kindred disciplines and established the important role that geology could play in archaeology.

Starting in the early 19th century, studies by geologists of ancient Greek and Roman marble quarries began to appear. In 1837 L. Ross described the quarries of Mount Pentelikon, near Athens. In the 1880s G. R. Lepsius studied many classical marble quarries and listed criteria for distinguishing each. Then, using these criteria, he named the marble sources for over 400 well-known statues in European museums. In 1898 the American petrologist H. S. Washington warned archaeologists that Lepsius's criteria were not infallible and that a great range of textures and minerals were to be found in each quarry. Again, these were warnings that scientific criteria should not be applied indiscriminately to solve archaeological problems. However, the caveats were not heeded and Lepsius's criteria were followed uncritically for the next 60 or so years. We know today, based on more-detailed, isotopic analysis, that many of Lepsius's identifications were incorrect

In 1905 Raphael Pumpelly, then president of the Geological Society of America, led an expedition to the Turkestan region of Siberia. His study of prehistoric sites was a pioneer effort to re-create paleoenvironments and served as a forecast of studies yet to come. Ellsworth Huntington, the eminent geographer, followed with similar studies at early sites in North and Central America and showed how geomorphic and archaeological evidence could be used to discern environmental and climatic change.

In the United States, arguments over artifacts and extinct fauna continued on well into the 20th century. In the 1920s and 1930s, E. H. Sellards, considered to be the first to practice geoarchaeology on North American sites, established the geological context of early human habitation near Vero, Florida, and near Midland, Texas. The so-called Midland Man (actually a young woman) is now known to date to 11,000 BC.

The paramount role of geology in archaeological studies today can no longer be debated. Prospecting to locate ancient buried sites uses geophysics and geochemistry. Geomorphology can point out the most likely places for ancient habitation and help to determine paleoenvironmental settings. After digging starts, stratigraphy and sedimentological methods determine the sequence unique to the excavation site. Geophysics helps again to locate and interpret the nature of buried features and to point out the most promising places for careful excavation for walls, buildings, and artifacts. Palynology (the study of ancient pollen) and phytology (the study of siliceous plant remains) can help decipher ancient subsistence and agricultural strategies and the paleoclimate.

Artifacts and human remains are analyzed chemically and isotopically; analysis of bone helps determine ancient diets and diseases. Geochemical, geophysical, and petrographic techniques provide the signatures needed to recognize the provenance of raw materials and to re-create the ancient technologies used to fashion ornamental and useful objects. These same techniques can help establish the authenticity of ancient artifacts.