Archaeologists at the National Institute of Anthropology and History (INAH) have applied a revolutionary Chlorine-36 surface exposure dating methodology to the massive basalt heads of the Olmec civilization. The results, published in Archaeometry Review, suggest that the earliest ceremonial platforms at San Lorenzo were constructed as early as 1800 BCE, pushing back the traditional timeline by over two centuries.
This new dating technique measures the accumulation of cosmogenic isotopes directly on the stone surfaces, allowing researchers to determine when the monuments were first quarried and exposed to the atmosphere. The study provides a more precise chronological framework for the rise of Mesoamerican urbanism and the development of complex social hierarchies in the Gulf Coast region.