Spanish administrative term
The term natural is defined by the mid of the 19th century by the Spanish administration as follows:
This name is given to the primitive Indians with whom the Spaniards settled the peace agreements, although their descendants had mixed by marriage, either female Indians with male Spaniards, or female Spaniards with male Indians, or female Indians with Chinese…
The term natural was a category used by the Spanish administration, to differentiate Chamorro islanders from other residents such as European, Spanish, Carolinians or Filipinos.
The term natural had no connotation other than to refer the person, either male or female, born in a certain province. Natural de Marianas refers to any person born in the Marianas, but nevertheless the term usually applied for Chamorros, so the expression Naturales de Marianas meant the indigenous population of Marianas, the Chamorros. It could also refer to a person of Spanish descent, whose birthplace was the Mariana Islands. For a person born in Marianas but whose parents were born in Spain, usually, but not necessarily, a further specification was used: Español, natural de Marianas.
For further reading
Diaz Arenas, Rafael. Memorias Históricas y Estadísticas de Filipinas y Particularmente de la Grande Isla de Luzón: 5ª entrega. Manila, 1850.