Uplift (specifically biological uplift) is the act of an advanced civilization helping the development of another species. The xel'naga carried out this process multiple times as part of their cycle of reproduction, choosing two species that possessed purity of essence and purity of form. After seeding life in the Milky Way, the xel'naga returned to the jungle world of Aiur and began uplifting the protoss. Over the eons, they watched and secretly molded them and then moving on to the zerg, but their plans went awry.
Ways of UpliftingEdit
The xel'naga utilized both genetic engineering and guidance to enhance species. In the case of the zerg it heavily emphasized the genetic aspects rather than the cultural and mental ones.
There are two ways of uplifting with several branches each: the indirect one, used in the creation of the protoss, who were largely left to mold their own civilization while secretly being aided and enhanced by the xel'naga, and the direct uplifting.
The direct uplifting was used in the creation of the zerg; almost every step of their evolution was cataloged and monitored. The xel'naga molded them into creatures without free will and bound to a single Overmind.
The attempted production of a hybrid between protoss and zerg by Samir Duran may be considered a form of uplift, but much different than the method used by the xel'naga which took millennia. The protoss dark archon, Ulrezaj, may have been attempting a form of uplift on vat creatures in the Aiur caverns of the Tal'darim cult.