Indigenous peoples of Mexico (Spanish: pueblos indigenas de Mexico), Native Mexicans (Spanish: nativos mexicanos), or Mexican Native Americans (Spanish: nativo america mexicanos), are those who are part of communities that trace their roots back to populations and communities that existed in what is now Mexico prior to the arrival of Europeans. According to the National Commission for the Development of Indigenous Peoples (Comision Nacional para el Desarrollo de los Pueblos Indigenas, or CDI in Spanish) and the INEGI (official census institute), in 2015, 25,694,928 people in Mexico self-identify as being indigenous of many different ethnic groups, which constitute 21.5% of Mexico's population.

The pre-Columbian civilizations of what now is known as Mexico are usually divided in two regions: Mesoamerica, in reference to the cultural area where several complex civilizations developed before the arrival of the Spanish in the sixteenth century, and Aridoamerica (or simply "The North") in reference to the arid region north of the Tropic of Cancer where few civilizations developed and was mostly inhabited by nomadic or semi-nomadic groups. Despite the conditions however, it is argued that the Mogollon culture and Peoples successfully established population centers at Casas Grandes and Cuarenta Casas in a vast territory that encompassed northern Chihuahua state and parts of Arizona and New Mexico in the United States. Mesoamerica was densely populated by diverse indigenous ethnic groups which, although sharing common cultural characteristics, spoke different languages and developed unique civilizations. One of the most influential civilizations that developed in Mesoamerica was the Olmec civilization, sometimes referred to as the "Mother Culture of Mesoamerica". The later civilization in Teotihuacan reached its peak around 600 AD, when the city became the sixth largest city in the world, whose cultural and theological systems influenced the Toltec and Aztec civilizations in later centuries. Evidence has been found on the existence of multiracial communities or neighborhoods in Teotihuacan (and other large urban areas like Tenochtitlan). The Maya civilization, though also influenced by other Mesoamerican civilizations, developed a vast cultural region in south-east Mexico and northern Central America, while the Zapotec and Mixtec culture dominated the valley of Oaxaca, and the Purepecha in western Mexico. The greatest change came about as a result of the Mexican Revolution, a violent social and cultural movement that defined 20th century Mexico. The Revolution produced a national sentiment that the indigenous peoples were the foundation of Mexican society. Several prominent artists promoted the "Indigenous Sentiment" (sentimiento indigenista) of the country, including Frida Kahlo, and Diego Rivera. Throughout the twentieth century, the government established bilingual education in certain indigenous communities and published free bilingual textbooks. Some states of the federation appropriated an indigenous inheritance in order to reinforce their identity. In spite of the official recognition of the indigenous peoples, the economic underdevelopment of the communities, accentuated by the crises of the 1980s and 1990s, has not allowed for the social and cultural development of most indigenous communities. Thousands of indigenous Mexicans have emigrated to urban centers in Mexico as well as in the United States. In Los Angeles, for example, the Mexican government has established electronic access to some of the consular services provided in Spanish as well as Zapotec and Mixe. Some of the Maya peoples of Chiapas have revolted, demanding better social and economic opportunities, requests voiced by the EZLN. The Chiapas conflict of 1994 led to collaboration between the Mexican government and the Zapatista Army of National Liberation, an indigenous political group. This large movement generated international media attention and united many indigenous groups. In 1996 the San Andres Larrainzar Accords were negotiated between the Zapatista Army of National Liberation and the Mexican government. The San Andres accords were the first time that indigenous rights were acknowledged by the Mexican government. The government has made certain legislative changes to promote the development of the rural and indigenous communities and the preservation and promotion of their languages. The second article of the Constitution was modified to grant them the right of self-determination and requires state governments to promote and ensure the economic development of the indigenous communities as well as the preservation of their languages and traditions. The Spanish legal system divided racial groups into two basic categories, the Republica de Espanoles, consisting of all non-indigenous but initially white Spaniards and black Africans, and the Republica de Indios. As there was greater intermixture and resulting offspring, a more formal casta system came into place, with specific terms for different racial mixtures. This system gave more political and social power to Spaniards so that Indigenous people and blacks could be kept in lower positions. When the ethnic origins of the person were not known, phenotypic characteristics were relied upon to determine the status of the individual. Those that were in lower statuses had to pay more to the crown. When Mexico gained independence in 1821, the casta system was eliminated as a legal structure, but racial divides remained. White Mexican argued about what the solution was to the Indian Problem, that is indigenous who continued to live in communities and were not integrated politically or socially as citizens of the new republic. The Mexican constitution of 1824 has several articles pertaining to indigenous peoples. The second article of the constitution of Mexico recognizes and enforces the right of indigenous peoples and communities to self-determination and therefore their autonomy to: V. Preserve and improve their habitat as well as preserve the integrity of their lands in accordance with this constitution. VI. Be entitled to the estate and land property modalities established by this constitution and its derived legislation, to all private property rights and communal property rights as well as to use and enjoy in a preferential way all the natural resources located at the places which the communities live in, except those defined as strategic areas according to the constitution. The communities shall be authorized to associate with each other in order to achieve such goals. Under the Mexican government, some indigenous people had land rights under ejido and agrarian communities. Under ejidos, indigenous communities have usufruct rights of the land. Indigenous communities choose to do this when they do not have the legal evidence to claim the land. In 1992, shifts were made to the economic structure and ejidos could now be partitioned and sold. For this to happen, the PROCEDE program was established. The PROCEDE program surveyed, mapped, and verified the ejido lands. This privatization of land undermined the economic base of the indigenous communities much like the taking of their land during colonization.

Using a quote from the above article, answer the following question: whats the procede program
The PROCEDE program surveyed, mapped, and verified the ejido lands.