1. We recognize that proper terminology in radiocarbon and obsidian hydration conventions is determinations rather than dates. For the sake of brevity, we use the latter term.
2. Radiocarbon dates in this paper were calibrated using the 1993 Stuiver and Reimer Radiocarbon Calibration Computer Program—specifically the decadal tree ring option of that program. The calibration yields a lo confidence interval of 68.3 percent, and a 2o interval of 95.4 percent. Radiocarbon spans are taken from the summary of minimum cal age ranges (cal ranges) and maximum cal age ranges as displayed on the calibration printouts for each sample. For conciseness the ranges are shown without the associated intercepts of the radiocarbon calibration curve. See Stuiver, M. and P. J. Reimer (1993) Radiocarbon 35: 215-230.
3. Wolfman’s date is unpublished because of his sudden death, but nicely supplements Rue’s findings. Braswell (1996: 537) is thus incorrect in asserting that there are no radiocarbon or archaeomagnetic dates from the Copan Valley later than a. d. 950 that suggest human presence in the valley after that time. (The radiocarbon dates were reported in Rue 1986, 1987; Webster, Freter, and Rue 1993; and other publications.)
4. Adjusted to the 1950 radiocarbon baseline; see discussion below.
5. Willey et al. (1994) have devised yet another version; it is very similar to Viel’s 1993 scheme, but does admit the possibility of the late use of Coner or Coner-like ceramics.
6. The Acbi/Coner transition is most marked by the obtrusive occurrence of highly distinctive Copador polychrome pottery. We emphasize obtrusive because the Copador tradition appears older elsewhere on the southeast Maya periphery, most notably at Ceren, El Salvador (Webster, Gonlin, and Sheets 1997: 55-56). Copador certainly long predates a. d. 600 outside the Copan Valley and could be expected to occur in small amounts as early as the sixth century at Copan.
7. A twelfth experiment, not relevant to the issues discussed here, was also carried out. It attempted to correlate two single events at Copan urban core group 9N-8. The results of the radiocarbon date were rejected as inconsistent with the context.
8. When reporting or interpreting displays of dates, many archaeologists fail to report outliers or dates that otherwise seem unacceptable. We include and evaluate all dates here.
9. Our latest hydration date is a. d. 1235. If correct, this date indicates that at least a few people were still living in the Copan Valley as late as the early thirteenth century. Of course it is very unlikely that this date represents any kind of terminal occupation, and new hydration dates or radiocarbon dates might well indicate even later human presence.
10. We were allowed to take no more than half of the obsidian in each lot for dating. This sampling limit affects the estimated occupational spans because few dates could be run for sites where little obsidian was encountered in test excavations. More samples will generally indicate greater time spans, although there is probably a threshold of diminishing returns in this respect.
11. Specifically, the hydration equation is:
((micron reading 2 hydration rate) x 1000)-baseiine date or 1985.
12. Interested readers may obtain a complete list of all dates of both kinds, along with radiocarbon laboratory numbers and details of intercepts for the radiocarbon dates, from the senior author on request.
13. Because Experiment C has neither a single intercept nor a central intercept, we split the difference between its two recorded intercepts (a. d. 670 and 685) and used a. d. 677 in our calculation.
14. A clumsily worded statement of ours (Webster and Freter 1990b: 81) has been taken to mean that we found Ulua polychromes associated with contexts dated as late as the thirteenth century. We meant to imply only that such ceramics long outlasted the royal collapse. This confusion is our fault. We never believed that such pottery was used later than a. d. 950-1000, and we thank Rene Viel for bring the misstatement to our attention.
15. Interestingly, Wolfman’s aforementioned archaeomagnetic date of a. d. 1100 comes from just such a large platform in the Las Sepulturas urban enclave. If this is an Ejar structure, it was used long after a. d. 1000.
16. Remember that the fact that most of the sites used in this experiment were not occupied much beyond a. d. 1000 is an artifact of our burial sampling, and so cannot be taken as support of Manahan’s asserted terminus.
World History
