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 questionable for a number of reasons: their small numbers, continuous intermarriage with non-African populations over various generations. Mexico did have slaves during the colonial period, although the institution was already in decay by the late 1700s. Througout most of the colonial period, the population of free blacks surpassed that of enslaved. As in other Spanish-speaking territories with black populations, including Spain itself, they were largely genetically absorbed by the majority. Slavery and ethnic categorization at birth (see casta) was abolished with Mexican independence and the creation of a national Mexican identity, especially after the Mexican Revolution, emphasized the notion of mestizaje whereby ethnic divisions among Mexicans were actively suppressed by the national ideology.