I was wondering how the instinct of self-preservation first arose in animals. I am particularly interested in the reason what drove animals to move when they gained the ability to do so, and what mechanism drove them to move towards nutrients and away from danger, since these rather primitive animals, it seems, lacked anything like a nervous system, and thus experienced neither deprivation nor discomfort or fear. (If I am wrong about this, please do not hesitate to correct me !)

Thank you very much for your answer !

Kind regards,


I think that phrasing the question in terms of instinct, discomfort and fear is perhaps misleading. Many organisms without nervous systems show quite complex behaviours and that include directed motile components coupled to sensory systems in the broadest sense. In fact, this is even true of cells not just whole organisms - think of human sperm "sensing" and "swimming" towards an egg. So emotional complexity of the sort your question alludes to is in no way a prerequisite for the evolution of movement towards attarctive stimuli, or indeed away from noxious ones (that could lead to damage/death).

I agree. In many ways rephrasing this around the mechanisms that provide "fitness" and thus survival is a better way of thinking about this.