Of course we can define it - instincts are stored action programs defined genetically, while learned programs that can be amended according to contextual cues are not. Humans, with abstract thought and language, do the latter far better than nearly all other animals. Heck, animals aren't even capable of directed episodic memory so it's doubtful they even entertain a narrative sense of self over time.
Nihilism is fine, and probably the true state of affairs, but so what? Once we decide we want to play in the ethical space, some things do get to count. And those are the things we think, not what chickens think (because they don't).
Actions are not defined genetically. All thought is abstract. All animals have language, even plants and bacteria do. Why would they not have "directed episodic memory" or "a narrative sense of self"? If nihilism, then why the appeal to utility? Teach me your mind reading techniques, they are truly impressive!