The Nu-Cosians came into existence through the process of bioengineering.
Genetic modification, also known as gene splicing or bioengineering, involved the scientific manipulation of a species' genetic code to achieve a specific outcome. The Nu-Cosian people were the result of bioengineering, specifically using genetic components derived from the Cosian species. Certain geneticists have proposed that the various related species categorized as the Delphidians were genetically modified into servitude by an ancient overlord. On Chrona, agricultural researchers Leo Leonis and his spouse Tepha dedicated their efforts to the creation of genetically-altered food sources, aiming to alleviate hunger among the population. The addition of prehensile tails to living beings was a popular trend on Coruscant during the Imperial Era, but these modifications were rumored to only last a few months. The seasonal presence of chewfly infestations once caused devastation on the Fruited Moon within the Hetzal system, until they were eradicated via genetic modification.
Following the demise and subsequent return of Darth Sidious, the Dark Lord of the Sith, the Sith Eternal followers resorted to gene splicing in their quest to engineer a suitable host for Sidious's spirit. Their trials involving his genetic blueprint resulted in the creation of numerous strandcasts, including a clone who was intended to be the Dark Lord's "son," but all were considered failures.