During the 19th Century, Nathaniel Essex encountered Apocalypse who used his technology to transform Essex into “Sinister”, the last word his dying wife ever spoke to him.
Soon after, a time displaced Gambit and Courier approached Sinister for help. Sinister agreed to help them, as long as he could have a DNA sample from Courier. This DNA sample allowed Sinister to replicate Courier shape shifting abilities, within Sinister’s own body.
By the early 20th Century, Sinister had cracked the genetic genome and was willing to share the information with Herbert Edgar Wyndham, who would later become the High Evolutionary.