Undo engram in ARK

You can use a mindwipe tonic to reset everything, stats and engrams. This is very useful on a normal server, less so on primitive if you happen to play primitive.

Other than that, you're stuck with what you choose. If you're a low level you could always just store your stuff in pin locked boxes (or with your tribe), create a new character, and get everything back.

Mindwipe tonics aren't super hard to make, but generally a waste of some important resources unless there's an engram you really need but can't afford, and you're a high enough level that leveling up would take too long. Once you get above level 70 though, if you're playing solo / with a small tribe on a normal server, you pretty much have to mindwipe a lot to get everything you need.

Here's a link for how to make one: http://ark.gamepedia.com/Mindwipe_Tonic