http://masseffect.wikia.com/wiki/N7
N7 are strictly members of the Alliance, hence human beings unless a miracle happens.
No telling what N7 means after the Reaper war, considering this:
N7 Special Ops Team
No species can remain neutral during the Reaper conflict. Allied forces are recruiting anyone, soldier or mercenary, smart, fast, and tough enough to survive galactic war. The most experienced operatives form squads to secure objectives, evacuate civilians, and battle Cerberus or the Reapers deep in enemy territory. Initially led by N7 Alliance marines, these squads have been nicknamed the N7 Special Ops. In light of these teams' exemplary service and remarkable bravery, the Alliance has allowed this unofficial name to spread across the ranks as a sign of respect for their efforts.
Wouldn't take much at all to make N7 an official interspecies branch, considering there are "N7s" of all shapes and sizes running around now.





Do góry





