Respuesta :
It started to not be afraid of death but to smile at it and honor their ancestors

Los orígenes de la celebración del Día de Muertos en México, pueden ser trazados hasta la epoca de los indígenas de Mesoamérica, tales como los Aztecas, Mayas, Purepechas, Nahuas y Totonacas. Los rituales que celebran las vidas de los ancestros se realizaron por estas civilizaciones por lo menos durante los últimos 3,000 años. En la era prehispánica era común la práctica de conservar los cráneos como trofeos y mostrarlos durante los rituales que simbolizaban la muerte y el renacimiento.El festival que se convirtió en el Día de Muertos cayó en el noveno el mes del calendario solar azteca, cerca del inicio de agosto, y era celebrado durante un mes completo. Las festividades eran presididas por el dios Mictecacihuatl, conocido como la "Dama de la muerte" (actualmente corresponde con "la Catrina"). Las festividades eran dedicadas a la celebración de los niños y las vidas de parientes fallecidos.
And translated to English:
The origins of the Day of the Dead in Mexico can be traced back to the time of the Mesoamerican Indians, such as the Aztecs, Mayas, Purepechas, Nahuas and Totonacas. The rituals that celebrate the lives of the ancestors were performed by these civilizations for at least the last 3,000 years. In the pre-Hispanic era it was common practice to preserve the skulls as trophies and display them during the rituals that symbolized death and rebirth. The festival that became the Day of the Dead fell in the ninth month of the Aztec solar calendar, near the Beginning of August, and was celebrated for a full month. The festivities were presided over by the god Mictecacihuatl, known as the "Lady of Death" (currently corresponds to "la Catrina"). The festivities were dedicated to the celebration of children and the lives of deceased relatives.And yes it is properly translated. I am fully bilingual. This is for more info. But a more resumed conclusion is same as other answer. I just gave you more info......