Terran scientists create “hemi-vectors,” hoping the added genetic diversity and resilience would help preserve the species. Genetic modification can be applied to creatures after they are born. MarsCo begins hemivector refugee program (adding useful supplies, workforce, information, etc.)
The creation of hemivectors lets humans become vectors. There are consequences to this innovation: a wave of vectors with Terran sensibilities can make the jump to Mars, bringing human values and ideals (for instance, this route lets many of the old Terran religions jump between planets), and problems (terrorists posing as vectors become a major problem within the year.)
While there are no numbers in the game book, and likely none recorded in Vector history, forced vectorization becomes one of the tools for wiping out the human race over the course of the Silent War.