Why isn't the upper limit of pain lower in humans?

Question

From what I understand, pain is an useful mechanism that signals us that something is not quite right with our body (in particular, we're under attack). It's good - it alert us and tells us that we got to do something (stop the threat, or run away, etc). From Wikipedia:

Pain motivates the individual to withdraw from damaging situations, to protect a damaged body part while it heals, and to avoid similar experiences in the future.

However, there are damages that cause too much pain. If you are stabbed in a particular place, you will most likely have so much pain that you simply can't fight back or run away. The shock makes it incredibly hard to do something or even think properly.

So my question is: is there a reason why pain can elevate to such high levels? I'm just assuming that if we had some sort of hard limit on the amount of pain we receive, we could perform better in several dangerous situations. In other words: instead of hurting so much that we can't even think properly, it hurts enough to let us know we are in grave danger but still capable of assess the situation and perhaps even act accordingly.

Obviously some physical damages will render you unable to act anyway. Like, damages on the spine that may cause your limbs to malfunction. But I mean damages such as a large open wound on the abdomen: if that didn't hurt so much, I'd imagine you could probably stand up and run away (you'd probably bleed out but at least you'll have a chance to escape the threat).

My guess is that it "cannot be helped". Pain are signals from different parts of the body to the brain, and once a signal is sent, the brain has no choice but to process it accordingly.

Answer 1

You are assuming that fighting back with a bad wound would be more useful than dropping to the ground. That is not always the case.

Dropping to the ground and ceasing activity is very adaptive in almost any situation involving potentially significant blood loss. Becoming prone or supine prevents loss of consciousness, the most critical aspect of survival. Decreased movement is also likely to decrease the rate of blood loss (though not in as significant a manner as consciousness).

Certainly with a significant abdominal wound, running would increase cardiac output, which would increase bleeding. Is running from a traumatic event advantageous if you pass out before escaping? On the other hand, lying prone and holding the wound (instinctive) may reduce bleeding and prolong consciousness and life.

What "cannot be helped" (like withdrawing a hand from a flame) is usually advantageous.

An infant's cry changes during circumcision (an involuntary reaction to pain). The cry in turn naturally produces a visceral reaction in nearby adults that compels action (causes a state of strong sympathetic nervous system activation.) The adult either avoids the cry by trying to distance themself, or responds by coming to the infant's cry.

The infant cannot help changing the intensity of the cry with intense pain. If a "certain level of pain" was as far as one could feel, the baby might not elicit the sense of urgency in adults which it does.

_{Newborn pain cries and vagal tone: parallel changes in response to circumcision.
ASSESSMENT OF INFANT CRY: ACOUSTIC CRY ANALYSIS AND PARENTAL PERCEPTION}