Knowledge of magnetism in ancient Mesoamerica: Precision measurements of the potbelly sculptures from Monte Alto, Guatemala

Archeological finds from Mesoamerica and elsewhere in the New World have yielded intriguing yet inconclusive evidence for an early appreciation of magnetism among Native American peoples. Here we use scanning and handheld magnetometers to map the distribution of magnetization on eleven basalt potbelly sculptures from the Monte Alto site, now housed in La Democracia, Guatemala, dating from second half of the first millennium BCE. Our 1 cm resolution magnetic scans, performed on four sculptures, reveal for the first time that they were originally magnetized by lightning strikes pre-dating the carving process. We quantify the area and morphology of the magnetic anomalies, demonstrating that the correspondence between magnetic anomalies on the sculptures and specific anatomical features is non-random at the P = 0.01 level, which is consistent with the qualitative conclusion of an early study by Malmström (1976). The apparently intentional colocation of carved anatomical features and pre-existing magnetized regions implies that the sculptors were able to detect the presence of anomalous magnetic fields, which may have been facilitated by lodestones similar to iron oxide artifacts and iron-ore mirrors. Our observations strengthen the case for an awareness of magnetism in the ancient New World.