It is possible to easily tame a giga as a single person tribe or on single player. All you need to do is to get it slightly stuck on a tree and then stay in agro range just enough that it still wants to eat you but doesn't try to bite the tree down. Then just knock it it with darts or arrows. I have used this method before and it is very effective.
I dare you to raise one!! They are savage if you got two high lvl parents (about lvl 140ish) and you get imprinting on it. The thing will become an adult with about 230% melee and basically one chomp any bronto!!! But on the down side you loose your job and your girlfriend
Make 4 metal dino gates and 1 large bear trap. Place three frames and door into an incomplete square and the large bear trap in the I between them. Lure the Giga into the trap and while its trapped place 4th down to make the square. Then just light it up with tranqs