Afro-Mexicans are an ethnic group that predominate in certain areas of Mexico, such as the Costa Chica of Oaxaca and the Costa Chica of Guerrero, Veracruz (e.g. Yanga) and in some towns in northern Mexico. The existence of black people in Mexico is unknown, denied or diminished both in Mexico and abroad for a number of reasons: their small numbers, heavy intermarriage with other ethnic groups, and Mexico's tradition of defining itself as a "mestizaje" or mixing of European and indigenous. Mexico did have an active slave trade since the early Spanish period, but from the beginning, intermarriage and mixed race offspring created an elaborate caste system.