The mystery of the Mayan civilization’s decline In spite of the fact the Mayan civilization disappeared many centuries ago, the mystery of the sudden fall of the successful and developed civilization which cultural achievements are still examined and discussed as significant ones remains to be one of the most controversial questions in the history. The results of the researchers’ investigations support the idea that the Mayan civilization was highly developed in comparison with the other civilizations of that period of time. The modern researchers still refer to investigating such cultural and religious achievements of the Maya as their calendar and ritual places as the sources of the special knowledge which is significant for the contemporary social life, culture and art. That is why the causes of the Mayan civilization’s decline are considered to be the most intriguing historical mystery. The theories of climatic changes and population’s density There are a lot of theories with the help of which historians and archeologists try to explain the fall of the Mayan civilization. Many researchers focus on various factors and determine such possible causes of the process as conflicts with the other civilizations, natural disasters and climatic changes, epidemic diseases and the fall of the ruling class. All these theories are supported by little evidence provided by the archeological researches. It is possible to concentrate on two theories which determine climatic changes and the problem of the population’s density as the main causes for the Mayan civilization’s disappearance. In 1983, William Folan presented his version of the Mayan civilization’s decline which depended on the problem of climatic changes (Folan et al., 1983). The archeologist’s idea was supported by Tom Abate who offered his discussion of the question with references to the hazardous climatic changes which made it almost impossible for the Maya to successfully adapt to the abrupt changes of the cool and warm climates (Abate, 1994). Moreover, the archeologists’ vision of the problem was based on the theory that the civilizations’ collapses in the Mesopotamian valley were also affected by the climatic changes (Sayre, 2012). The next significant theory was developed by Billie Turner in 1976. The geographer examined the archeological data and concluded that the Mayan civilization disappeared when the population density at the territories occupied by the Maya reached its maximum point. The process had the extreme meaning for the development of the civilization because the Maya began to suffer from the lack of the cultivable land, their cropping techniques were ineffective, and the progress in agriculture could not address the needs of the civilization anymore (Turner, 1976). The reasons for the theory of population’s density as the cause for the Mayan civilization’s decline Billie Turner’s theory which is based on the issue of the population density can be discussed as more appropriate for explaining the mystery of the Mayan civilization’s decline in comparison with the theory worked out by Folan and Abate because Turner examined the factual archeological data from the point of the correlation between the number of the Mayan population and the territories’ carrying capacity. Moreover, the main principles of Turner’s theory can be discussed as independent for explaining the mystery of the Maya when Folan and Abate stated that their theory’s ideas can be discussed with references to the other influential fa