ECOLOGICAL AND GEOCHEMICAL ARCHAEOLOGY IN THE SOUTHERN MAYA LOWLANDS' URSULA M. COWGILL AND G. E. HUTCHINSON INTRODUCTION AYAN PEOPLES occupied the southernmost portion of the Yucatin M Peninsula and developed one of the highest known indigenous cultures of the New World during the first millenium A.D. This culture collapsed before 1000 A.D. and the Peten, as it is now known, never regained either the level of civilization nor the population it once is supposed to have supported. Other Mayan groups living to the north and south of the Peten underwent various types of cul- tural disturbances but generally there was no permanent depopulation in these areas. It would appear therefore that the population that once lived in the Peten presents a rather special case. It is presently thought that this population virtually disappeared. A number of hypotheses attempting to explain the cause of the collapse of Classic Maya civilization have been proposed. The purpose of the subsequent dis- cussion is to review such ideas in the light of research that has been carried out in the southern Maya lowlands, namely El Departamento de El Peten, the northern- most state of Guatemala. STATEMENT OF PROBLEM The excavation of any large aboriginal site invariably brings forth the prob- lem of attempting to estimate the size of its prehistoric population. One way of arriving at such an estimate is to determine presently the number of people the land can comfortably support and then extrapolate back in time. During the 1 The present contribution, designed to give a summary of such of our results as bear on archaeological problems, is based on a paper presented as part of the symposium, Pollen and Prehistory, held at the Society of American Archaeology, May 3, 1963, Boulder, Colorado. A full account of the study of the Bajo de Santa Fe is in press, while the cores from Laguna de Petenxil will be published in detail shortly. The initial field work was supported by a fellowship obtained by Dr. George L. Cowgill from the Henry L. and Grace Doherty Charitable Foundation, Inc. All subsequent field work and laboratory studies have been supported by grants from the National Science Foundation (Grant nos. 17831, 15606 and 8916). The lake cores here described were taken by George and Ursula Cowgill. Dr. George L. Cowgill was extremely helpful in many aspects of the agricultural study. Mr. A. L. Bump of the United Fruit Company materially aided the transportation of equipment and personnel to and from Guatemala and we are also grateful to Mr. Dana Condon, 267 VOL. 19, 1963 268 SOUTHWESTERN JOURNAL OF ANTHROPOLOGY excavation of Chichen Itza, a number of people, Emerson (n. d.) , Emerson and Kempton (1935) , Kempton (1935), Steggerda (1941) and Hester (1951, 1952, 1953, 1954) , carried out various types of agronomic studies in an attempt to ar- rive at some workable estimate of prehistoric population size. Steggerda (1941) was primarily interested in the problem of yield decline with continuous cultivation. He established four experimental plots, noted their yield and took soil samples yearly from 1933 to 1938. One of these plots was used as a control, allegedly virgin bush; another was a garden plot that was kept free of weeds and allowed to produce two annual crops; a third was a plot that had been cropped and was allowed to revert to bush; and the fourth consisted of a corn field that was planted annually during this period. Chemical analyses were performed yearly on soil samples taken from these plots. The decline in yield with increasing cultivation was not reflected in concurrent decreases in soil nutrient levels, and hence it was presumed that weed competition and possibly factors such as disease and climate were responsible for the noted decline. Steggerda was obviously unable to arrive at any other conclusions from the data given him; unfortunately, however, graphing such data as a function of the year, it was noticed that for some years a given element was low in all plots and other years it was high. This strongly sug- General Traffic Manager for Central America of the same company, without whose assistance the field work objectives would never have been realized. Sr. Carlos Samayoa Chinchilla, Director of the Instituto Nacional de Antropologia e Historia in Guatemala City made available the many excellent facilities of the museum. Sr. Francis Gall of the DirectiOn General de Cartografia provided access to aerial photo- graphs of the Peten region which proved to be extremely helpful during field work. Licenciado Jorge Salazar V., acting secretary of the Ministerio de EducaciOn POblica, helped procure authorization to bring field equipment into Guatemala. The Rev. and Mrs. Stanley Storey of the Nazarene Mission in Santa Elena, El Peten, as- sisted in taking one of the cores from Lake Petenxil, helped make contact with some milperos in some communities and were kind enough to collect lake, river and rain water samples for analyses. We are very grateful to Dr. Jaime Litvak of the Instituto de Prehistoria in Mexico City for his assistance in obtaining some of the statistical data reported in the population study, and to the authorities of the DirectiOn General de Estadistica in Mexico City for making available their excellent library and its facilities. Dr. Francis Kukachka of the Forest Products Laboratory in Madison, Wisconsin was kind enough to examine charred material from both the pit dug in El Bajo de Santa Fe and cores from Laguna de Petenxil. Dr. John Reeder of the Biology Department at Yale University assisted in the identification of some charred plant tissues found in the cores from Laguna de Petenxil. Dr. G. K. Voigt of the School of Forestry at Yale University was kind enough to allow the use of his Kjeldahal apparatus. During the few weeks stay at Tikal, Dr. William R. Coe and Mrs. Vivian Broman de Morales were always generous with their assistance and equipment. ECOLOGY AND GEOCHEMISTRY OF MAYA LOWLANDS 269 gests that the study really involved the variations in ability of the technicians em- ployed to perform chemical analyses from year to year rather than a real variation brought about by cultivation. Emerson was inclined to believe that the decline in yields was brought about by weed competition, while Kempton on the basis of a survey made in northern Yuca- tan felt that successive cropping caused a notable decline in fertility and hence also in yield. He suggested that the first crop received more fertilizer in the guise of ashes than the second year, and as a consequence the latter would be less productive than the former. The results of these investigations carried out in the northern portion of the Yucatan Peninsula unfortunately have been extrapolated to all of Middle Amer- ica to explain population decline and agricultural problems in general, despite the fact that this portion of the Peninsula is rather different from the southern part. The data presented by early agronomic workers unfortunately do not agree with one another. If the yield decline on successive cropping is due to weed compe- tition, presumably weeding would increase the productivity. If, on the other hand, the decline is due to a decrease in soil fertility, it has been supposed that only ferti- lizer could alleviate the situation, and as far as is known there was no pre-Colum- bian source. Despite the scientific confusion, one hypothesis that has appeared attractive to some archaeologists has remained in the literature, namely that the Classic Maya collapse was due to misuse of the land. Underlying all hypotheses concerned with cultural collapse of the ancient Maya is the attitude that slash and burn agricul- ture is harmful to the soil, that it makes an inefficient use of the land, and that it is basically incapable of supporting adequately any population of large size. Cooke (1931, 1933) and Ricketson (1937:11) on the basis of a pit dug in a seasonal swamp near Uaxactun, known as El Bajo de Joventud, concluded that there had been an intensive and excessive use of the land, bringing about denud- ation, excessive erosion and subsequent filling up of the bajos, which they believed had at one time been large lakes. Had these seasonal swamps once been lakes, they would have provided fish for food and a means of transportation, solved the present day problem of a shortage of dry season water, and perhaps have provided a more salubrious environment than today. The pit is described as having a 2.05 m. thick black layer of clay containing, at Uaxactim, a smaller proportion of calcite crystals than the underlying layer, which consisted of equal parts of paler clay and calcite. The presence of the black layer is interpreted as evidence for a period of intensive erosion brought about by 270 SOUTHWESTERN JOURNAL OF ANTHROPOLOGY overuse of the land. Cooke states that this black layer is similar to the soils found in the upland regions. Bullard (1960) accepts the hypothesis that the bajos were once lakes and also thinks that some portions of the larger ones were still open water at the beginning of the Classic Period. He doubts that their silting up was the principal reason for the collapse of the civilization, since sites along streams, rivers and modern lakes which could not have suffered from water shortages and other effects of silting also suffered decline. A somewhat different hypothesis, also involving the idea of the misuse of land, had been put forward by 0. F. Cook (1909, 1921) somewhat earlier. He concluded that the agricultural system in Yucatin was adapted only to the support of sparse populations. He presumed that, once the population reached a certain density, the resting period of the forest would become too short and that as a result frequent overburning of forested areas would destroy the forest, encourage the encroach- ment of perennial grasses, and hence make the land impossible to plant and crop in view of the primitive system then used.