Episode 4: The Survivors
Scenario 11: Old Friends (very last one)
Non spoiler quick explain: in the last scenario where Jess is hanging off the bridge, ignore her and go for the can on the ground. ;)
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This is a story changer so you may want to reload for the better ending after getting this one if you do this first (you evil person ;p). When I got this at least there wasn't even an ending for it, just the boat sailing off and cut, not even credits.
In one of the last scenarios of the last episode where you meet up with T-rex again, Jess is trapped hanging off a ledge. Two choices will present themselves. One button press on Jess and one on the can of dino DNA on the ground.
Choose the can to have this achievement pop and say a sad farewell to Nima.
Choose Jess for the Do-you-think-he-saurus Rex achievement.
Choose wisely. ;>