|Photo by Bjørn Christian Tørrissen, courtesy of Wikipedia.|
The Angkor, or "Classic", period of this civilization begins traditionally with the assumption of the title of chakravartin, or "universal ruler", by Jayavarman II in A.D. 802, and continues to A.D. 1431, when, according to the Royal Chronicles, a 19th century official history of dubious reliability, the Thai sacked the capital city of Angkor. Unfortunately, the tropical climate of Cambodia has meant that all written documents that date back more than 200 years, inscribed traditionally in palm-leaf books, have rotted away, leaving historians having to reconstruct Angkor's history from laconic monumental dedicatory texts on stone temples, which obviously give a very distorted view of the past and were never meant as the basis of histories, either. These dedicatory texts do provide the basic outline of a history of the Angkor period, however, and what is interesting is that despite later kings reckoning the foundation of their kingdom from Jayavarman II's ritual in 802, there are no contemporary inscriptions until 880, when the Preah Ko temple was dedicated. The last inscriptions at Angkor that can be dated are from the reign of Jayavarman IX (also known as Jayavarman Paramesvara), who took the throne in 1327.
Thus the Ankgor period begins in 802, and is in full gear by 880, continuing to ca. 1330/1340 and finally fading out in the 15th century. Interestingly, this corresponds very well to a 'Dark Age' in ancient Maya civilization. The Classic Maya civilization is pretty much defined by the use of the Long Count calendar, and the earliest Long Count date in the Maya Lowlands dates to A.D. 292 and the last to A.D. 909. However, the Classic Maya world went into a major crisis shortly after A.D. 800 and the next century saw sites fading out, with the final population in most cities gone entirely by A.D. 1000. The Early Postclassic period is attested at hardly any sites and not until the rise of Mayapan and other sites, such as Topoxte, in the 13th and 14th centuries do we see much evidence of Maya civilization. Thus, at just the time that the Classic Maya went into the crisis that would ultimately consume their civilization, we see the rise of the Angkor period in Cambodia.
This inverse correlation exists even for the earlier period of both cultural areas as well. The height of the Classic Maya civilization is the Late Classic period, especially the 8th century. This period in Cambodia, however, is one in which few temples were constructed and inscriptions are few and far between. There are a number of pre-Angkor inscriptions found throughout the rest of Cambodia. The earliest are undated but appear to date to the 3rd and 4th centuries A.D. Dated pre-Angkorian inscriptions are relatively abundant from 611 to the beginning of the 8th century, but are almost non-existant for the subsequent century and a half. The period of most intense carving of pre-Angkorian inscriptions in Cambodia, then, is during the 7th century, which corresponds quite closely to the famous hiatus period of the southern Maya lowlands.
Now, I would not take these correlations too strongly - the hiatus at Tikal ends in the 690s while at sites such as Palenque and Copan it ends even earlier, by the 650s. However, it is interesting to see that the general ups and downs of Maya and Angkor civilizations do seem to be the inverse of each other. Michael Coe has written about comparisons between the Maya and Angkor civilizations and while he thinks there may have been direct contacts between the two regions, I do not see any evidence for such contacts. Therefore, I cannot see this inverse correlation between the two regions' cultural histories as being directly related. However, I do wonder whether general trends in climate change around the globe might not be at least partially responsible. Last year Brendan Buckley and his colleagues published their study on the ancient climate of Cambodia, and have proposed that Angkor was hit by two severe droughts, one in the mid-14th century and a second in the early 15th century, which were followed immediately by extra-severe monsoons. These extreme climate disasters overtaxed the civilization of Angkor and led to the abandonment of the city's famous irrigation network of canals, and ultimately to the move of the capital city to the southeast. You can read a popular article of their research here, and you can see their more academic publication in the Proceedings of the National Academy of Sciences here. In my dissertation I argue that the Classic Maya Collapse was largely due to similar changes in climate and that while there is evidence for accompanying warfare and social changes, these were more results than causal factors of the Collapse.