Did I not learn to fear knife-wielding assailants?

I'm in the editing phase of the first draft of Fear and Fight: Understanding Our Natural and Learned Responses to a Threat.

Conventional wisdom suggests that our natural responses to a threat is a fight-or-flight, stress (Siddle's survival stress), fear response. I did not experience either when I was confronted by a knife-wielding assailant on two separate occasions. These natural responses to a threat were selected for in nature because they conferred a survival advantage on an individual. Where was my fight-or-flight/stress/fear response when my survival was threatened on two separate occasions. That is the question that drove Fear and Fight.

Our natural responses to a threat are based on an unconscious evaluation or appraisal of a stimulus. A lot of my work is driven by Robert Plutchik's psychoevolutionary theory of emotion. He proposes n emotion process model with 'inferred cognition' being on of the components at the front end. Plutchik proposes 10 postulates about cognition in relation to psychoevolutionary theory of emotion. Postulate #6 is:

In higher animals, most cognitions depend on learning and can be modified by experience.

 Humans have very few innate fears. What innate fears we do have relate to stimuli experienced in our evolutionary past. Knife-wielding attackers were not a stimuli in our evolutionary past environment. Is the answer to my question that I'd never learned to be scared of knife-wielding attackers?

Many authors discussing fear in battle suggest that its normal to be scared in battle. After all, our survival is threatened in battle. They suggest only a fool would not be afraid. But how does that fear come about? Are they suggesting the intellect makes a conscious determination that the people firing at me can kill me and this becomes the internal stimulus for the emotion/amygdala which responds with fear?

Are we afraid in battle because we've been socialised; taught fear. Stories of injury and death, seeing the injured and dead, the injured and dying - is that what teaches us to be afraid?

I can imagine the Australian Aboriginals when they first came into contact with the white British pointing their long sticks at them would not have been afraid. They were not holding them as if they were going to throw them and they didn't have pointy tips. After the first loud bang and puff of smoke and seeing their comrades fall injured or dead, I'm sure they quickly learned to fear these white men with funny sticks.

Do we have a natural response to expressive anger-aggression by another? This may be why I didn't experience fear because both of my assailants were quite calm and measured.

This work that I'm undertaking provides plenty of food for thought.