A Middle Archaic archaeological site on the west coast of Mexico

The Cerro de las Conchas shell mound, located on Mexico's south Pacific coast, was formed between 7,500 and 6,000/5,500 years ago, during the Middle Archaic period. Few Mesoamerican coastal sites are as early or have been studied so intensively. Limited diversity in the artifact assemblage and faunal origins, the presence of bedded strata, and the absence of features associated with permanent residency indicate that the site was used intermittently as a processing station for aquatic foods. Seasonality studies on clam shells suggest that this occurred year round. The site likely was situated initially adjacent to a brackish water lagoon near a tropical rainforest because faunal studies indicate a strong focus on lagoonal taxa, whereas a forested environment is indicated by phytoliths. Toward the end of the Middle Archaic, however, an increase in faunal and artifact richness, an emphasis on fauna with a tolerance for marine conditions, and phytolith evidence for more disturbance vegetation compared to earlier times, may be due to marine transgression. Later, pottery-using agricultural peoples used the site for farming and possibly residency. This example of early human adaptation to a coastal environment of Mesoamerica permits a corrective to previous research that is weighted heavily in favor of upland sellings. Copyright