"The building material for the villages and cities of the IVC [Indus Valley Civilization] was predominantly mud brick. Only in the Mature phase were baked bricks used in quantity, especially for walls and floors exposed to water (Possehl, 2002; Datta, 2001). This phase of baked bricks coincides with the urban phase of the IVC, with many large cities as opposed to the predominant village settlements before and after the Mature phase" (p.1) write the authors. This leads them to characterize in this article, which nicely lays out the facts about Indus bricks, that the "chronological dynamics of brick usage by typology . . . and a new point of departure for discussing the possible reasons for the mysterious decline IVC decline" (p. 1).
Although mud bricks date back to Mehrgarh, baked bricks were a hallmark of the Indus civilization, and the authors discuss their benefit: "Baked bricks are less affected by long-term water exposure; this water resistance became a key fac- tor in the expansion of Harappan villages and cities into the Punjab flood plains. Their sustained establishment in the flooding zones of the river plains was facilitated by baked brick technology. The protective function of baked bricks is exemplified by the massive and technically refined flood protection structures around Mohenjodaro and Harappa (Kenoyer,1998). Baked brick usage for all buildings in the flood-prone city Chanhudaro demonstrates the importance of baked-brick technology for flood protection" (p. 4).
Indeed, the authors see baked brick technology as an important constituent of the "Harappan urban mind" and related, at least chronologically with technologies like writing and shell ornamentation, suggesting that the standard dimensions that underlay much of the baked brick industry (a largely but not exclusively 4:2:1 length:width:height ratio, for example) as being part of the social and elite-controlled norms that underlay social structures.
This leads to their summary point, which is not that environmental degradation is what led to the decline of Indus cities, given the wood needed to sustain a baked brick industry, for example. They conclude: "We provide here a novel integrative view of IVC site distribution, its urban-rural contrast, and the dynamics of brick usage and urban size to find new points of departure for interpreting the IVC decline. We find that despite a large geographic change of the site distribution, the number of sites and—to first approximation—population does not change much between the Early, Mature, and Late phases. Urban area and baked bricks, however, change dramatically in the material culture, as do their social counterparts administration, elite structure, and religion. By concentrating on the cities, we point to primarily social reasons as a starting point for further investigations on the IVC decline" (p. 9).
Image: Bricks at an unexcavated mound, Harappa