In the early twentieth century, astronomer A.E. Douglass sought to correlate cyclical variations in solar activity with climate records by examining annual growth rings in timber. Because trees in the arid American Southwest are exceptionally sensitive to yearly rainfall variations, Douglass observed that trees of the same species growing in the same climatic region during the same decades produced nearly identical patterns of wide and narrow rings. By matching overlapping sequences of rings from living trees of known age with the inner rings of older logs, Douglass established a continuous, year-by-year chronological sequence extending back several centuries. Consequently, when archaeologists excavated prehistoric wood beams from ancestral Puebloan masonry dwellings, Douglass was able to identify the exact calendar years in which those architectural timbers were felled by comparing their ring sequences to his established regional chronology.
Based on the passage, which of the following statements regarding the excavated ancestral Puebloan wooden beams is most strongly supported?
- They were cut from timber species that exhibited yearly growth ring patterns corresponding to regional rainfall variations.Answer
- BThey could be accurately dated only after archaeologists had independently determined the precise decade the dwellings were abandoned.
- CThey survived in the archaeological record primarily because builders treated the exterior surfaces with chemical resin sealants.
- DThey exhibited growth ring widths that remained completely uniform regardless of annual shifts in environmental moisture.
- EThey originated from timber harvested exclusively in distant wetland ecosystems outside the American Southwest.