Why do butyric acid and carcases, both non-pathogenic, have such repulsive odours?

 (writing in progress)
 
It is an odd biological fact that both butyric acid (which I suggest we call vitamin M) and rotting carcases produce smells to which the human olfactory system is sensitive, and which are perceived as repulsive.

What do readers think the reason might be?
 
Butyric acid is vital for human health. Yet, in any quantity this stuff smells repulsive, i.e. of vomit, stinky feet, etc.

Of course, it is possible that the same substance in tiny concentrations can smell attractive (as used in the food industry). However, that would not explain why it smells so repulsive in large concentrations.

This is because a substance does not have a smell as an intrinsic property. Rather, the smell is a matter of perception. In adaptive terms, bad odour indicates that there is a good reason for the human body to avoid the substance in question.

Since butyric acid is not toxic, what could the reason possibly be?
 
Along similar lines is the stink of rotting corpses.

A dead body, after a certain period of decomposition, smells in a striking way. It is one of those stinks that is hard to ignore, being perceived by the human mind as deeply offensive and disturbing.

But again, this is a biological anomaly, because there seems to be no good reason why we should react in this way.

There is little that can infect one from coming close to a carcase, however rotten. There is no pathogen, as far as I know, that ‘jumps’ from a carcase to a human in its vicinity, e.g. by means of spores or viruses.

Even if one is infected by some pathogen from a dead body, it is (as far as I know) invariably a pathogen that was present in the living body, and tends to wane after death – as opposed to a microbe that only arises after death and causes the stink even as it threatens to infect those approaching the carcase.

If someone is infected with AIDS, TB, gangrene, etc., it is generally safer to touch them after death than before death. This is because the only things that can infect one from a dead person are the pathogens that were present in life (and which possibly contributed to their death). These tend to vanish once they die, although there is some lag time (reputedly up to 6 days, in the case of AIDS).
 
So, as in the case of butyric acid, rotten carcases stink out of all proportion to the threat they pose to the owner of the offended nose.
 
Can readers think of a plausible rationale of cause and effect here?

My initial suggestion:

It is adaptive to be reminded that people or other animals have died, so that one can avoid succumbing to the same cause, regardless of whether it is a pathogen or not.

I.e. when a carcase stinks, the smell is a message to the effect that ‘something killed someone, watch out’. This is as opposed to ‘I stink because I contain microbe that threaten to infect you, too’.

The carcase stinks just the same if the person was healthy until killed by violence. Perhaps one's nose could be alerting one to the risk of violence, rather than the risk of pathogens of decomposition?
 
But, if so, how would this work in the case of butyric acid = vitamin M?

(writing in progress)

Publicado el julio 27, 2022 12:33 MAÑANA por milewski