Bear with me guys.
This is the lead up.
just put this track on a loop while reading...
https://www.youtube.com/watch?v=zpv5kFMcq8I

So...
I'm pretty good with a big knife,
a rapier,
and a short / court sword,
a mace,
(plenty of classes ..plenty of training over my life..)
even the bow and rifle on the farm...
even good in hand to hand close quarters...
and now I heartily suggest everyone of my friends here get real good too at killing and staying alive.
Never have I ever had to say this....
But...
In this circumstance ..
It isn't a wrenching moral or ethical dilemma...
'Cause sure as ***** runs out of a goose...
If you don't kill your doppelganger ...
He is going to kill you...
and we wouldn't even know you were gone.
No ***** here now my friends...
Existential Threat-Level : Imminent.
Got some time yet...better hone some killin' and defendin' skills.
Survivin' wouldn't hurt either....I have a slew of first aid certs. incl. wilderness...
Never hurts...

http://www.express.co.uk/news/scienc...ntually-HUMANS
(disclaimer: granted it ain't the most reputable rag for this epic news)