The Gaddang people are a linguistically identified ethnic group of related families sharing lengthy residence in the watershed of the Cagayan River in Northern Luzon, Philippines. Gaddang speakers are reported to number around 30,000, plus another 6,000 genetically related Ga’dang speakers whose vocabulary is more than 80% identical.
These two groups are often depicted in historic and cultural literature as a single population; distinctions between (a) the Christianized “lowlanders” and (b) the non-Christian residents in the mountains appear to be ignored by many sources. There are both intriguing similarities and unreconciled differences in history, location, lifestyle and beliefs between these two related populations. (Gaddang | Wikipedia)