Final humans?

I played subnautica 2(obviously) and after a bit I was thinking, when they say “you’re the last of humanity” do they actually mean the last in the entire universe? It may be because I haven’t gotten that far in the game yet but how did the entire human race go extinct? Did I miss something in the previous games? Will it be answered later in the game? As of making this the only possibility I can think of is that when we release Alan in below zero he’s the one who causes it.