Do we have any info from lore or cannon about these guys? Like we know they're reaching the Mojave and all that but were they spliced? did they evolve? What exactly are they? Could they be a new type of alien that lost their ship or a form of alien? I mean these guys are interesting but seem widely unknown about compared to other fallout enemies.

Nothing as far as I could tell.

The common consensus is they're Hopeville/Ashton survivors when the Bombs fell that were mutated by the radiation. http://fallout.gamepedia.com/Tunneler#Background

Thanks MArtyr I just wish we knew more about them

That does not really say a whole lot. Just mutated by radiation. And it does not say when they started to be like they are.

My money is on "Think Tank experiment" but all we really have is speculation from Ulysses / the Courier.