In the most recent issue of American Antiquity (76:3), there was a focus on osteoarchaeology: both human and mammal. Watts, White and Longstaffe in the article “Childhood Diet and Western Basin Tradition Foodways at the Krieger Site, Southwestern Ontario, Canada” discuss the use of stable isotope analysis in order to determine dietary habits. Using this data, they are able to draw conclusions beyond diet, arguing for changes in maize production, breastfeeding and go so far as to challenge the notion of sedentism co-occurring with horticulture.
Stable isotope analysis has been used frequently by American archaeologists in order to aid in determining the advent of maize horticulture. While alternative evidence like macrobotanicals and phytoliths from cooking residue has also aided in this interpretation, stable isotope analysis of human remains continues to be one of the most valuable indicators. The problem with a large amount of dietary evidence, including faunal and macrobotanical remains, pollen, phytoliths, pottery residue, and coprolites is that this is indirect evidence of what was available and what was being processed, but not necessarily what was being consumed. Using stable isotope analysis can reveal what the individuals found at a site were eating.
Stable isotope analysis can measure a number of different isotopes that are carried in bones even after an individual has passed away. Nitrogen 15 and carbon 13 are the most highly used for determining diet. Nitrogen is often associated with marine diet, and carbon with a land diet. Carbon can be further broken down into C3 or C4 pathway plants. They differ in the photosynthesis process, and can be differentiated in the skeleton to see what types of foods individuals were consuming. C3 plants are more widely found, with those that most interest archaeologists including rice, wheat, rye, barley, cassava, potatoes, algae, spinach and yams. C4 plants range less widely than C3, and includes maize, sorghum, sugar cane, millet and papyrus. Given that C4 plants are more limited in their territory, when C4 percentage is high within a body it can be fairly easy to predict what type of plant the increase in C4 was caused by. When carbon 13 is measured, it is displayed in parts per million, with C4 ranging between -9 to -16ppm and C3 ranging between -22 to 35ppm.
Watts, White and Longstaffe (2011) analyzed human remains from the Krieger site in the Western Basin in Southwestern Canada, an area where maize introduction and dietary lifeways are less well known. The site under examination dates to the Late Woodland/Western Basin Tradition (1000-1550 CE). Previous work examining this period had determined that during the 11th to 12th centuries that the Western Basin lacked the evidence for transition to maize horticulture even though there was significant change directly south of them in both settlement and subsistence. Archaeologists argue that the Western basin sites continued a pattern of caching resources and seasonal mobility, and dietary evidence from indirect sources shows a mixed subsistence of marine, faunal and gathered floral that coincides with seasonal mobility interpretations. However, there is considerable macrobotanical evidence for maize even though the sites lack a semi-sedentary pattern of mobility that is usually associated with maize horticulture.
At the Krieger site there were 54 discrete pit features found, two of which contained human remains of 11-12 individuals. One tooth was removed from the maxilla of 10 individuals, including 3 adult males, 3 adult females, 1 sub-adult and three unspecified adults. By using stable isotope analysis of the teeth, archaeology were able to determine the dietary patterns as well as breastfeeding traditions of the individuals from the Krieger Site and compare them against other sites. The percentages of C4 (evidence of maize) at Krieger was -7ppm, which is comparable to studies done of pigs fed on a diet of 74% maize. They also found that there was no evidence of weaning in the dentition, which would be marked by differences in nitrogen and carbon levels in different teeth due to differences in trophic level. They argue that this is evidence of early weaning, and the placement of young children on an adult diet.
Using the lack of evidence for a strong weaning period and a lack of difference in the isotopic levels of males and females, Watt, White and Longstaffe (2011) argue that this type of pattern reflects those found in horticultural and agricultural societies where there is no division of labor and everyone works on maize production. Combining this with a lack of evidence for sedentism means that the population was moving to a maize based horticultural subsistence pattern but not a sedentary settlement pattern. The limited sample of human remains and stable isotope analysis does limit the interpretation. However, the combined use of archaeological and osteological evidence does make a strong argument for their case.
Sedentism: This is the change from a nomadic or mobile settlement pattern to one where groups are living in more permanent structures. A semi-sedentary pattern means that the group was moving infrequently or by the changes in season.
Horticulture: This is the preparation and maintenance of gardens and small scale farms, versus agriculture which occurs on a much larger scale.
Watt, White and Longstaffe. 2011. Childhood Diet and Western Basin Tradition Foodways at the Krieger Site, Southwestern Ontario, Canada. In American Antiquity 76(3)
Hirst. About: Stable isotopes in Archaeology. About. http://archaeology.about.com/od/stableisotopes/qt/c3c4cam.htm
Thanks to Kristina Killgrove for some corrections to the blog post!