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The stalagmite MC01 was recovered from Macal Chasm cave on the Vaca Plateau of Belize in 1995, and an initial paleoclimate interpretation was published in 2007. Additional uranium-thorium ages have extended the paleoenvironmental record back from 3250 to 5250 cal yr BP, and the stable isotope (δ18O and δ13C) record is dramatically improved by 660 new values. A series of major dry events (MDEs) evident in stable isotopes, ultraviolet-stimulated luminescence, and petrography began ~ 3100 cal yr BP, and the initiation of these events coincides with an increase in El Nino dominance and southern shift in the Intertropical Convergence Zone. Three MDEs, centered at 1750 cal yr BP (200 CE), 1100 cal yr BP (850 CE), and 850 cal yr BP (1100 CE) and found in other regional climate records, coincide with Maya sociopolitical changes. Residuals from regression of δ13C versus δ18O are interpreted as a proxy for maize cultivation and land clearing, with residual values gradually increasing at the start of Preclassic Period settlement (3950 cal yr BP/2000 BCE), peaking after 2250 cal yr BP (300 BCE) during major Maya development in the Late Preclassic and Classic Periods, and dropping to pre-Preclassic values after regional land abandonment (~ 850 cal yr BP/1100 CE). Regional Maya population growth and cultural expansion may have been aided by abnormally low precipitation variability, as stable isotope variability suggests the Late Preclassic through the Late Classic was the most stable precipitation regime of the past 4000 years. This additional research on MC01 complements other regional paleoenvironmental records that suggest that MDEs coincided with disruptions in Maya society from the Preclassic through the Postclassic Periods. Although it is clear that not all significant sociopolitical changes can be attributed to the MDEs, these events likely played an antagonistic role in social stability.

Caves were used as ritual venues by the ancient Maya from the Early Preclassic to the Postclassic period. These sites have been intensively investigated, but little research has been devoted to changes in cave use over time. Work at Chechem Ha Cave in western Belize investigates transformations in ritual practice occurring between the Early and Late Classic periods using an explanatory framework that incorporates high-definition archaeological research with a paleoclimate reconstruction derived from speleothems. This is one of the first projects to directly link these data to the archaeological record. We also introduce new methodology to evaluate changes in ritual practice using use-intensity proxies and artifact patterning. These data demonstrate that Late Classic transformations were coeval with climatic drying. The phenomenon was identified in this case study, and the pattern is prevalent throughout the eastern lowlands suggesting that an ancient Maya drought cult was initiated at this time. We provide the first evidence that there was a failed ritual response to environmental stress, implying that a loss of faith in Maya rulership contributed to the downfall of political systems. This is an important finding for collapse theories that include ideological causations.

Paleoenvironmental data from a stalagmite from western Belize provide a 3300-year record of droughts that impacted the Maya civilization at least four times across a span of 1500 years, and the most sustained period of drought coincided with the collapse of Classic Maya civilization. The stalagmite, which comes from Macal Chasm in the Vaca Plateau, provides reliably dated reflectance, color, luminescence, and C and O stable isotope records for the period from 1225 B.C. to the present. The record thus encompasses the Maya Preclassic, Classic, and Postclassic periods. The Maya civilization peaked in population density and socioeconomic complexity during the Classic period extending from A.D. 25 to 900, but it declined abruptly over the years from A.D. 750 and 900. The stalagmite record indicates that a series of droughts, which collectively form the most prolonged dry interval in the 3300-year record, lasted from A.D. 700 to 1135 and thus coincided with the collapse of the Maya civilization. In addition, two earlier droughts evident in the stalagmite record coincided with the Preclassic Abandonment and the Maya Hiatus, two earlier declines in Maya civilization. A drought in the mid-1400s recorded in post-Classic documents is also evident in the stalagmite record. Collectively, these findings illustrate the dependence of Mayan civilization on water supplies and the impact of declining water resources on a vibrant civilization.

Analysis of a stalagmite from northwestern Botswana shows that variation in the abundance of detrital grains, which can be conveniently approximated by gray-scale measurements, provides a potentially valuable paleoclimatological record. The stalagmite, which is from near the mouth of Drotsky's Cave, is largely spelean CaCO3. It nonetheless also contains detrital grains of quartz, clays and iron oxides, carbonates, and other minerals. The abundance of those detrital materials varies along the stalagmite's growth axis. Analysis of the positions of those grains indicates that they preferentially accumulate in the dry season. Gray scale (a measure of the lightness or darkness of the cut speleothem) is inversely correlative with detrital content and thus with periods of decreased rainfall. It also correlates positively with historical records of rainfall and with rates of speleothem growth, which are controlled by rainfall. Gray-scale measurements from this speleothem can thus serve as a proxy paleoclimatologi...

Rats were given six acquisition trials, one trial a day, in a straight alley with either an ascending or a descending series of varied reward magnitudes. In accordance with expectations from sequential theory, the subjects that were trained with an ascending series were more resistant to extinction than the subjects that were trained with a descending series.