It's not the sense of self. What is your sense of self? It's all the sensations arising from the field of consciousness: the apparent localized 'personal' visual field, the apparent localized 'personal' auditory field, the apparent localized 'personal' sensational (touch) field, and etc.. These don't cease to exist when ego is no more, but yes.. without the sense of self - ego may not be able to exist. It's not thoughts/mind. If your mind is quiet because of some meditative state you're in - that doesn't mean that ego is no more. Ego is not mind activity. Thoughts are also just one of the sensations arising from consciousness: call it the mental field if you want. But it's also not localized nor is it personal. It's not a biological or psychological feature.  The ego doesn't originate from the human form. Yes I can see how the human form has played a role in its creation but it's not responsible for it. Other people don't have egos, your ego is the only present ego until you die. Animals or other creatures don't have egos. EGO IS ATTACHMENT It's the attachment to imaginary form. Attachment is you right now believing/thinking that you're separate, that you're an individual. You are attached to the idea of being a separate self. Ego is not the idea of a separate self, ego is your attachment to that idea. Become aware of this and transcend ego. Ego death is literally the death of ego and not anything else, it's detachment and unification with Being.   If you find something unclear from what I wrote then you're free to ask questions, otherwise go do self inquiry. Meditation helps too! ?