Public Release: 

Skill Key To Level Of Complexity

Penn State

Nashville, Tenn. -- The number and type of mistakes made while manufacturing obsidian blades may help archaeologists to better understand the social and economic structure in ancient Mexico, according to a Penn State anthropologist.

"Theoretically, a craftsman who makes blades often, should be more skilled than one who makes blades infrequently," says Bradford W. Andrews, graduate student in anthropology in College of the Liberal Arts.

"So, if we look at the aggregate skill exhibited in a workshop, we should be able to rank the workshops according to how much time the specialists spent and by looking at this variation in labor, shed some light on the economic complexity of early state societies," he told attendees today (April 3) at the annual meeting of the Society of American Archaeology in Nashville, Tenn.

Andrews looked at obsidian excavated in 1993 from five workshops at Xochicalco -- a site near Cuernavaca -- and some collected in the 1960s from the surface of workshops in Teotihuacan -- just outside Mexico City. These sites were occupied between A.D. 150 and 950.

Traditionally, archaeologists use location and obsidian debris density per unit area to rank workshops. The workshops from Teotihuacan are divided into domestic or non-domestic, with non-domestic considered specialized private or state institutions and domestic divided into local or regional workshops. Local workshops are considered part-time, and regional workshops are considered full-time operations.

"If we can further rank these domestic workshops, identifying different forms or modes of production functioning at the same time, we could understand more details about early economic complexity," says Andrews.

Obsidian blades are found throughout Mexico in great numbers. These blades are made by shaping a chunk of obsidian into a core that is a faceted cylinder with one flat end -- the platform -- and the other end narrowing to a rounded point. Using pressure flaking, the craftsmen placed a wooden tool on the edge of the platform between two facets and applied constant force, separating a blade from the core.

Typically, obsidian blades range from 3 to 8 inches in length and are between a quarter and half inch in width. The blades are straight and have a rhomboidal cross section.

Of interest to Andrews were blades, blade fragments and cores. From experiments with making obsidian blades, he knew the types of mistakes most likely to indicate a lack of skill.

"I'm looking at four measures of skill -- hinge terminations, distal plunging blades, plunging termination height and final core diameter," says Andrews.

Hinge terminations occur when a blade stops part way down the core. Usually, blades attempted after that will end at the termination scar. Distal plunging blades curve under the end of the core rather than coming off straight. They shorten the core and make all subsequent blades shorter. The plunging termination, or the height of the extra material removed with a distal plunging blade is an indication of the severity of the error. Final core diameter is a measure of how much the craftsmen tried to conserve materials and how skilled they were.

In the Xochicalco workshops, the highest skilled workshop matched that predicted by conventional methods as did the lowest skill level workshop. However, the three remaining workshops showed an intermediate range of skills.

The Teotihuacan samples were very small and even after grouping them only the core artifacts had sufficient numbers to be significant. Another problem is that surface collecting may have preferentially increased the size of the artifacts in the sample.

"Some of the variation in the Xochicalco workshops may be due to variation in the activities emphasized at each workshop," says Andrews. "For example, distal plunging blades occur with smaller cores, but if larger cores are discarded, there will be fewer distal plunging blades."


EDITORS: Mr. Andrews may be reached at (814) 865-0907.

A'ndrea Elyse Messer
(814) 865-9481 (office)
(814) 867-1774 (home)

Vicki Fong
814-865-9481 (o)
814-238-1221 (h)

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