Andrew D Atkin:
Some time ago, as an experiment, lions were introduced into Australia to see how they would cope (Australia had lions in ancient times). As it happened, the lions had no problem at all catching and eating kangaroo's that were basically defenseless and plentiful. The interesting result was with the way the kangaroo-bounty affected the lions behaviour.
The groups of lions, who were normally rivals, lost their territorial instinct and started socialising with each other. This is clear evidence that lions are not a territorial species by default. Territorialism for lions is a secondary response to food scarcity. So, when lions have a given degree of anxiety about food, this in turn translates to tension which induces territorial reactions to other groups of lion.
This is a good example of a sophisticated relationship to primary instincts in a higher animal. A more basic territorial species would not react like the lions. They would be territorial regardless of the environmental conditions. The lions, much more sophisticated, have an environmentally-responsive switch that turns territorialism on or off, depending on the circumstances.
Humans are of course the most sophisticated species of all. In turn we should have the most sophisticated relationship to our instincts. And clearly we do. When the living is good humans are placid and reasonable, when the living is tough we become reactive and harsh. Violence, cruelty, craving for power and domination, indifference and self-centeredness etc, etc. are behavioral traits linked to stress and insecurity. Sure, they are human traits and they're perfectly natural in themselves, but they only become manifest insofar as the environment switches them on.
[Please note, the environment can be--and to varying degrees always is--psychologically internalised from childhood. This is the story of neurosis, and it explains why an immediate change in the environment does not always lead to an appropriate change in behaviour.]
What this means:
My message to evolutionary psychologists is to please stop theorising as though the human brain doesn't have a neocortex. The neocortex clearly communicates with the primal brains (brainstem and limbic system), leading to sophisticated instinctive responses to the environment. And human instinct is not weak, it simply has many switches.
However, we can see why psychologists sometimes think in a context as though human instinct has a mind of its own, in isolation to the reasoning neocortex. This is because it often does operate in blatant isolation to the neocortex.
Example: Take a man terrified of flying in a plane. He knows full well that his fear is irrational, but he can't help being terrified anyway. This instinctive reaction is coming from the triggering of old traumatic material in his mind, and the reason why his neocortex can't tell his brainstem to "shut up" is because the link between the two brains (neocortex and brainstem) is literally severed, in part, due to the function of repression*, and so the brainstem in this case becomes excited in isolation to higher-level cognition.
Indeed, it is the highly neurotic individual (compulsive, and somewhat out of control) that we find ourselves describing as "acting like an animal". Can I correct that? "Acting like a more primitive animal".
And this is what evolutionary psychologists need to appreciate (and study). Thinking in ignorance of trauma-imprint theory (here) is inducing them to make some false deductions on human behaviour, and the role of our ancient instincts. For example, it was asserted by some psychologists a while back that we feel terrified talking in front of groups because it reminds our ancient brain of the threat of tigers. Nope - the human brain is not that dumb. It has more to do with the threat of personal exposure and humiliation, which is a feeling more heavily exaggerated in some people than others due to childhood imprints in this area.
*The generating source of the over-reaction is fully isolated from the neocortex (repressed) and likewise cannot be muted by the neocortex.