It stands to reason that any sort of policy or idea usually benefits one group over another. The beneficiary usually is the group that creates the policy in the first place. In the case of Spain's colonial empire, it is the people born in Spain that benefited from the social stratification of the New World.
The Spanish when colonizing the areas formally belonging to the Native Americans wanted to make one message clear: Our culture is superior to your own.
Perhaps they were intimidated by the engineering feats of the Inca and the Aztec empires. Indeed, they were one of the most centralized of Native American tribes.
At the top of the social hierarchy were what were called the peninsulares, or Spanish born. Think of the Spanish as being born on the Iberian peninsula and you'll see why they are called peninsulares.
The assumption is that these peninsulares are all of light complexion and therefore easily identifiable as being the creme de la creme of this social hierarchy in the New World. You'll see why in a bit.
Next on the social ladder are the creoles, or descendants of Spanish born parents. These are individuals who are considered socially inferior to the peninsulares simply based on where they were born, in the New World.
Top government jobs were reserved not for the creoles, but for the peninsulares. This would lead to social conflict in the future as enlightenment ideas crept into the minds of learned creoles who then questioned the status quo.
The peninsulares or Spanish born who came to the New World obviously did not find an unoccupied land with no culture to call its own.
Native to the New World were Native Americans as diverse if not more diverse than the Europeans themselves. As said earlier, these Native Americans were used as slaves of the Spaniards forced to work under the encomienda system enabled by the Spanish King and Queen. Having no standing army in Spain to defend and sustain this newly established empire, Spaniards were granted the right to use Native Americans to labor in the New World in search of gold and silver, and to provide Spain with the raw materials needed to bring wealth to the Mother Country.
In order to justify such enslavement then, Native Americans needed to be seen as less in the eyes of the Spanish born. When the abuse became so bad that a friar by the name of Bartolome de las Casas complained about it, the Native Americans were then replaced with Africans to continue to the exploitation of the New World. This is why pure Native Americans and Africans were considered to be the lowliest within the caste system set up by the Spanish Crown.
However, we then have the question of the mestizos and mulattos. What about them? Perhaps the reason they are one step above the pure Africans and Native Americans is because they have a hint of European blood within them. Whereas the creoles were discriminated against simply because of where they were born, the mestizos and mulattos were discriminated against based on who they were.
Domination of the Native and African groups could be forced by the Spanish with labor systems or by race mixing. By blending Native blood with European blood and bringing into the New World the mestizos, Native Americans have an incentive to identify with their colonizers as is the case with the mulattos who were a mix of African with European blood.
Perhaps even the bottom rung of the social hierarchy, the pure Africans and Natives, were given the opportunity to give in to their colonizers by bearing their children. Thus the forgering of the Native and African cultures would solidify the presence of the Europeans forever.
This racial division was intended to keep a system of labor going. So I wonder sometimes, given the reality of which groups sometimes have the majority of the wealth, is this still true today?