43 M.B. Schiffer, The Archaeology of Science, Manuals in Archaeological Method,
Theory and Technique 9, DOI 10.1007/978-3-319-00077-0_4,
© Springer International Publishing Switzerland 2013
Experiments yield knowledge about a wide range of subjects that contribute to archaeological recovery, analysis, and inference (for recent overviews, see Coles 1979 ; Cunningham, Heeb, and Paardekooper 2008 ; Ferguson 2010 ; Mathieu 2002 ; Millson 2011 ; Saraydar 2008 ; Shimada 2005 ; Skibo 1992 , chapter 2). Archaeologists also do experiments to illuminate the science of prehistoric societies.
This chapter presents examples and case studies that illustrate two experimental approaches for modeling a technology’s scientifi c generalizations: (1) replication or imitative experiments (Ascher 1960 ), which produce recipes, empirical generaliza-tions, and experimental laws, and (2) controlled experiments that yield experimental laws (Schiffer et al. 1994 ).
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research may still produce a valuable partial or skeletal recipe (e.g., Frison and Bradley 1980 :51–52). Let us now turn to several idealized steps for modeling a manufacture recipe.
1. Infer the raw materials. For ceramic and metal artifacts, this information is supplied by petrography, neutron activation analysis, electron microprobe, or other archaeometric tools (see chapter “Contributions of Archaeometry”).
Zooarchaeologists can often identify the element as well as the genus or species from which a bone artifact was made.
2. Learn where in the environment the raw materials occur(red). The sources of ground and chipped stone are revealed by a geological survey as are sources of metal ores, clay, temper, and pigments, augmented by archaeometric analyses.
The distribution and prevalence of modern fauna hint at which species might have been available, at least for historic times and later prehistory. In well-known regions, information about raw material sources may already be in the literature.
Visits to source locations provide samples for experiments, and produce empiri-cal generalizations.
3. Infer basic manufacture activities by seeking distinctive traces, perhaps through archaeometric analyses (e.g., Malainey 2011 ). Thus, microscopic inspection of a polished metal section may supply information about annealing, cold- hammering, amalgamating, and other treatments. For pottery, petrographic analysis, dilatom-etry, refi ring, and differential thermal analysis are used to estimate the original fi ring temperature, which has implications for how fi ring was carried out.
4. Infer the tools that might have been used in the manufacture process by drawing on the following lines of evidence, when available: (1) traces of manufacture on the artifact itself, (2) tools found in the same site assemblage or in the region, (3) tools associated with the artifact in special contexts such as a burial, cache, or workplace, and (4) waste products and by-products of manufacture. Behavioral chain analysis sometimes provides inferences about which tools performed spe-cifi c interactions, even if they are absent from the immediate archaeological record (Schiffer 1975 ). Analysis of use-alteration traces on suspected tools may furnish supportive evidence.
5. Draft a recipe consisting of a sequence of interactions among artisan, tools, and raw materials.
6. Follow the recipe and assess the outcome.
A successful replication meets the following conditions: (1) relevant attributes of the replicated artifact are essentially identical to those of the original specimens, (2) waste products and by-products of manufacture match those from the archaeologi-cal record, and (3) use-alteration traces on the tool(s) match the archaeologists’
expectations. In practice, the fi rst and second conditions are often taken to be defi nitive.
Early trials often fail, and so replication is usually an iterative process. A failure leads to tinkering with the recipe, as in substituting different materials, tools, or interactions. Often, however, the problem stems from insuffi cient practice, as many manufacture processes have a rather steep and lengthy learning curve. It may require
Contributions of Experimental Archaeology
several years of part-time practice to become a profi cient potter or fl int knapper, for skill is acquired only through repetition and the fi ne-tuning of interactions.
As successive iterations begin to show consistency in meeting the conditions for success, we may claim to have created an accurate model of the recipe. We are well aware, however, that a claim may falter in the face of equifi nality because it is pos-sible—in principle—for different tools and interactions to replicate a given artifact (Ascher 1960 ). In practice, a recipe is likely to stand until challenged by an equally successful alternative. To distinguish between recipes, we may examine new attri-butes of the artifact, waste products, and tools; even then, arriving at a defi nitive recipe may be impossible. Nonetheless, differences in competing recipes may be judged trivial by archaeologists not invested in the replications.
Many recipes of prehistory are incomplete because we seldom fi nd evidence of ritual activities that might have occurred between or alongside technical interactions (see chapter “Varieties of Scientifi c Knowledge"). One hypothesis furnishes some guidance: when the outcome of an interaction or activity is uncertain (a probability somewhat less than 1.0), the artisan may have performed a ritual to ensure a suc-cessful outcome. Firing pots and smelting metals are failure-prone activities that may be highly ritualized. If ethnographic or ethnohistoric accounts of manufacture- related rituals are available, the archaeologist may hypothesize their occurrence and seek any subtle traces.
Experimental Laws and the Modern Era of Flintknapping Experiments
While conducting a replication study, the archaeologist learns the consequences of particular interactions—i.e., rediscovers the underlying generalizations. A simple example comes from heat treatment of chipped stone. Early ethnographies that mentioned the heating of stone prior to chipping were once dismissed as fanciful because no modern knappers used this process and because archaeologists them-selves were unfamiliar with it. During the 1960s and 1970s, Don Crabtree and oth-ers tried different heating regimes and assessed their effects on fl akeability (e.g., Crabtree and Robert Butler 1964 ). They found that heat treatment improves the fl akeability of certain materials by increasing its brittleness. Further experiments showed that heat treatment also affects a stone’s color and luster. By seeking the latter traces in prehistoric assemblages, archaeologists have shown that heat treat-ment was practiced by many an ancient knapper. Built into their technologies, then, was an experimental law: heating certain kinds of stone using a specifi c regimen (low heat, perhaps beneath a camp fi re, applied for many hours) makes the material easier to chip into projectile points, knives, and so forth.
The heat-treatment example is typical: the earliest attempts to replicate a specifi c technology usually resulted in the recognition of causal relationships that may be represented as experimental laws. Thus, William Henry Holmes, who in the late
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nineteenth century was among the fi rst researchers in the USA to replicate bifacially chipped stone tools, originated several generalizations that remain valid today. With words and a drawing he described the interactions by which a person can use one cobble to strike a fl ake from a second cobble: “Grasping a bowlder [i.e., cobble] in either hand (supposing bowlder hammers to have been used), the fi rst movement was to strike the edge of one against that of the other at the proper angle to detach a fl ake (Fig. 10)” (Holmes 1897 :59). Holmes’ drawing shows the relative position of hands and cobbles, and also indicates the “proper angle” of the blow. As noted in chapter “Varieties of Scientifi c Knowledge,” an empirical generalization or experi-mental law underlies each interaction in a recipe and makes a specifi c outcome probable. Because these generalizations are implicit in the technological tradition, they are unlikely to be elicited from an artisan (Schiffer and Skibo 1987 ).
Although the roots of fl intknapping experiments are centuries deep (Johnson 1978 ), the modern era began in the 1960s on both sides of the Atlantic. The need for experiments arose because the few remaining knappers in traditional societies used only the most rudimentary techniques whose science was inadequate for modeling the recipes of more challenging technologies. In France, prehistorians François Bordes and Jacques Tixier became expert knappers and stimulated widespread inter-est in replication. In the USA, Don Crabtree, a self-taught knapper, revived interinter-est in chipped-stone technologies and, in summer fi eld schools, passed along his knowl-edge to dozens of archaeologists (Whittaker 1994 ). This heightened activity yielded numerous recipes for many artifact types and, importantly, a host of explicit experi-mental laws. Crabtree, for example, studied the projectile points from Snaketown, a large Hohokam site in southern Arizona. In a series of experiments he easily repli-cated these artifacts (Crabtree 1973 ); his publication also furnishes numerous experimental laws, and so is an excellent primer on fl int knapping. A more complete compendium is Whittaker ( 1994 ).
There are four major fl aking modes: hard-hammer percussion, soft-hammer per-cussion, pressure fl aking, and indirect percussion. Each mode produces fl akes and debitage (waste products) whose modal properties can be described by statistical generalizations. Hard-hammer percussion, involving a stone hammer (e.g., Holmes’
experiments), detaches large, thick fl akes, as in the earliest stage of roughing out a tool. Hard-hammer fl akes generally have a prominent bulb of percussion on the ventral (interior) surface. Requiring a thick piece of antler or bone, soft-hammer percussion removes smaller and thinner fl akes that usually lack a prominent bulb of percussion. Final shaping and fi nishing may be done with pressure fl aking in which an antler tine, for example, applies pressure to the edge of the piece and removes a tiny, thin fl ake. In indirect percussion, a punch of bone or antler is held against the piece and struck with a hammerstone. This fl aking mode enables the application of much force to a very small spot and allows a larger fl ake to be pushed off than by pressure fl aking.
Once steeped in these generalizations and after a good deal of knapping practice, we can analyze a chipped-stone assemblage and often construct a skeletal recipe of the fl aking activities that produced particular artifacts. By following the recipe, we can test these inferences through experiments, fi lling in details of the interactions.
Contributions of Experimental Archaeology