Research TOC DATING ARCHAEOLOGICAL MATERIALS William L. Anderson colleague asked my laboratory to undertake the radiocar- bon dating of a bone from a human skeleton recovered Anear the town of Kennewick, Washington. This skeleton exhibited some very interesting features. Upon initial examination of the physical characteristics of the skull and other bones, the first impression was that it was the skeleton of an early European set- tler in the Pacific Northwest. Europeans had first arrived in that region at the earliest only in the late 1700s. However, on closer inspection, a stone projectile point that in other contexts had been dated as old as 8,000 years in this area was found imbedded in the pelvis of the skeleton. How could an ancient artifact be found in a skeleton that appeared at most to be only several hundred years old? A radiocarbon date would provide the answer as to the age. When the date was obtained, it turned out that the skeleton dated to the ninth millennium B.C. This result catapulted the Kennewick skeleton into both the popular press and subjected it to close scien- tific scrutiny. What were the implications of having a skeleton that did not appear to be Native American in appearance present in the New World at such an early time period? Could a group from Eura- sia distinct from the people whose descendants are the modern Na- tive Americans have entered the New World very early? “How old is it?” is one of the most frequent questions that visitors to museums ask when viewing archaeological objects. When news- papers report on the discovery of a supposed new fossil ancestor of our species, almost inevitably the suggested age of the fossil is men- tioned in the first paragraph of the story. When results from an exca- vation at an archaeological site are discussed, the question of “how old?” is almost always one of the first questions posed. The interest- ed public are most curious about how long ago a fossil lived or an ar- tifact was used. Professional archaeologists and paleoanthropologists are also concerned with the age of archaeological materials. This is because one of the purposes of archaeological research is to examine the evolution of human cultures over relatively long periods of time.1 CHRONOLOGICAL FRAMEWORKS Chronology orders the sequential relationship of physical events by associating these events with some type of time scale. Depending on the types of materials for which temporal placement is required, dif- ferent types of time scales have been developed. Geochronological (geological) time temporally relates elements of the physical struc- tures of the earth’s solid surface and buried features, documenting a 17 18 RESEARCH FRONTIERS 4.5 to 5.0 billion year period. The paleontological time scale orders the physical remains (fossils) of once living organisms and thus must cover at least the last 500 to 600 million years. The paleoanthropological time scale involves the fossil record over about the last 5 to 6 million year period documenting the evo- lution of the Hominidae (hominids), the group of bipedal primates of which we (anatomically modern Homo sapiens) are the only extant species—all others having become extinct. The archaeological time scale temporally orders the physical remains (artifacts) and features reflecting hominid behavior over at least the last 2 million years. Fi- nally, the historical time scale involves a period of time—not more than about the last 5,000 years—during which a few human societies have documented their activities with textual (written) data whose meanings, at least in part, can be deciphered. Different historic and scientific disciplines require and utilize chronologies using vastly different time scales. However, a fundamental distinction of particular significance in archaeology involves relative ordering or relative dating in contrast to chronometric dating. Relative ordering places events in a temporal sequence—namely, earlier than or later than—without specifying any temporal scale that specifies how much earlier or how much later. Chronometric dating applies a specif- ic time scale utilizing some fixed-rate mechanism the defined time is based on, for example, observable recurring natural phenomenon (e.g., earth rotation [day] or revolution [year]) or physical principle (e.g., ra- dioactive decay) in the case of a physical dating method. The primary basis of chronology building in most historic or text- aided archaeological contexts is dependent on the recovery of vari- ous types of documentary or inscriptional data or materials. Such text-based data is used to provide chronologically significant infor- mation such as sequential listing of rulers or officials, sometimes in association with the interpretation of notations of a calendar system or in relationship to some astronomical event that can be securely dated on the basis of modern calculations. The scholarship required to undertake the study of textual source data most directly involves the ability to decipher the symbols used to record the language and assign meaning to these symbols. Al- though there are notable exceptions, in most cases, the principal pur- pose of archaeological excavation within such contexts is to recover complementary evidence or supplementary textual data reflecting a society whose cultural and political history have already been doc- umented in existing texts at least in broad outline. In contrast, the principal basis of chronology building for text-less or prehistoric societies is the artifact record itself together with asso- ciated materials reflecting the depositional and environmental con- DATING ARCHEOLOGY MATERIALS 19 texts of the material culture of these societies. Primary chronologies are constructed based on analysis of the artifacts, the geological or pa- leoenvironmental contexts from which the artifacts are recovered, and the application of various instrument-based chronometric meth- ods, such as radiocarbon dating.2 CHRONOLOGY IN ARCHAEOLOGY One of the major advancements in scientific understanding of the nat- ural world has been the progressive unfolding over the last two cen- turies of an understanding of the geological history of our planet including the most recent geological periods during which our species (Homo sapiens) came to occupy a dominant position in the natural world. With few exceptions, until the early nineteenth century, tradi- tional Western concepts of time and thus chronology were tightly constrained by the cosmological world view reflected in the Judaeo- Christian Bible as interpreted by theologians and scholars of the me- dieval and early modern Christian Church. In the absence of a knowledge of any other data thought to be relevant, the Hebrew Cre- ation and Noahian flood narratives along with the genealogical data contained in Genesis were considered chronologically authoritative and capable of providing reliable chronological data that could be employed in tracing human history back to “the beginning.” In this sense, within such a framework, for the Western world until less than 300 years ago, the entire period of human presence on earth was con- ceived of as being historically documented.3 Literary scholarship linked the chronological data contained in the Biblical narratives with post- and extra-Biblical historical sources to create a traditional Western historical chronological framework ranging over some 6,000 to 7,000 years since the assumed original Creation. In the English speaking world, the best known example of such a traditional chronological synthesis was that developed by the seventeenth-century English scholar and churchman, the Anglo-Irish Archbishop of Armagh, James Ussher. His dates for important tra- ditional events in Hebrew history (e.g., the Creation, Flood, and Ex- odus) were included in the margins of the Biblical text, beginning with a 1650 reprint of the original text of the 1611 “Authorized” or King James translation of the English Bible. His calculations set the Creation event at 4,004 B.C.4 Developments beginning in early nineteenth-century geology and paleontology were largely responsible for the profound transforma- tion of Western consciousness concerning the temporal dimensions of 20 RESEARCH FRONTIERS both earth and human history. By the middle of the nineteenth cen- tury, with the creation of a sense of “deep time” for earth history, ge- ological chronology or geochronology was now conceived in units of hundreds of millions of years. The most recent geological periods were associated with the development of humankind, in part due to the first evidence of human fossils (e.g., Neanderthals) and the asso- ciation of what were assumed to be artifacts with fossils of a number of extinct animals. By the middle of the nineteenth century, prehisto- ry had emerged as an area of concern for a type of archaeologist who took up the task of providing chronological frameworks for this un- charted period. The strategies and approaches that were employed were, in large part, directly borrowed from what had been developed by geologists and paleontologists, rather than from the views and per- spectives of literary and historical scholarship.5 Almost two centuries of geological field studies combined with a wide ranging array of analytical data available over the last few decades have created a detailed chronological framework for the earth sciences, paleontology, oceanography—and archaeology. A number of specialized areas of scientific study have especially con- tributed to the progressive development of chronological frameworks documenting the period of time that human populations have been a part of the natural environment on earth. Only the last few percent of the geological column is chronolog- ically relevant to the period of time spent on earth by our species (Homo sapiens) and our immediate biological and cultural ancestors (earlier members of genus Homo, such as Homo erectus, and the vari- ous species of Australopithicus, and a possible ancestral hominid, FIGURE 2-1 CHRONOLOGICAL RELATIONSHIPS OF HOMINID SPECIES IN THE LATE TERTIARY AND QUATERNARY PERIODS DATING ARCHEOLOGY MATERIALS 21 Kenyanthropus platyops) (Figure 2-1).