In certain regions of Central America, the Aztec Day of the Dead has survived Christianity's attempts at assimilation.
The ancient Aztec Day or Days of the Dead was the target of systematic attempts at assimilation by the Christian conquerors of Latin America. However, unlike the Celtic festival Samhain, the Day of the Dead was more successful in resisting these efforts at incorporation.
The precise origins of “Los Dias de los Muertos” are lost in the shadows of prehistory. Possibly it goes back to the Olmecs, a civilization of south-central Mexico but dominant throughout the region from 1200 to 400 BC. The Olmecs are the progenitors of many Mesoamerican or Middle-American cultures, like the Aztec, Maya, Toltecs, and Zapotec, Mixtec, etc.
We can more clearly trace the festival to the Aztecs, who governed the region from the 14th to the 16th century. They called themselves Mexicas (hence “Mexico”). They commemorated the dead for the entire month of Miccailhuitontli (end of July - beginning of August), which was presided over by the goddess Mictecacihuatl, the Lady of the Dead, and Huitzilopochtli, the god of war. It was a joyous occasion, much like it is now.
The landing of Columbus in 1492/1498 marked the beginning of the European colonization of Latin-America. In 1519 the infamous Cortez invaded the Aztec empire, conquering it in 1521. In the wake of the Conquistadors came the Spanish, Catholic priests – though there already were Christian missions in Nueva España before the conquest, which it was their purpose to facilitate.
Obviously, when Christianity and Aztec religion met, it was not on even ground. Compare this to the situation within Europe, where Christianity grew gradually and organically alongside the old European pagan religions, mingling with them, rather than conquering them, before it became dominant. This may account for the compatibility of a festival like Samhain with Christian sensibilities.
The Aztec Days of the Dead, on the other hand, was much less appropriately respectful for the dead. The priests were shocked by its joyousness, colorfulness and its mockery of death. To rein it in, they shortened the month-long celebration to two days and moved it to coincide with their own All Saints’ and All Souls’. Then they imposed on it the spirit of the latter.
The results of these efforts vary greatly. In Puerto Rico, for instance, the Days of the Dead conform more to All Saints’. But in Mexico and Central America, the original tradition survives, especially in rural parts where the indigenous identity is strong.