I know other animals feel this same urge too (i’ve read that you can make a horse urinate if you make it hear running water, although i don’t know why you’d want to do that).

If it’s right, you should also feel a similar urge to urinate if you SEE water, and if you DRINK water.

There’s a limitation to the first one, though. Running water is healthier than still water (sorry, i don’t know what you call it, English isn’t my native language). So seeing RUNNING water could make a difference.

The whole effect could be less than hearing water anyway (because it sounds easier for Evolution to carve a neural path that relates to the SOUND of running water than its SIGHT, which would require a more complex set of parameters).

My hypothesis could be saved even if we can’t recycle urine in any way if:
a) We could do it in a distant past.
b) It’s good to make room in the bladder for new urine.

But why do we keep urine in the bladder anyway?

Well, why do we? Why don’t we pee in little amounts all the time?

Even if i was right, there are some elements clearly missing from the equation.

I’ve read that we have it, but i don’t trust my source.

It’s also possible that we once had it and we lost it before losing this lingering response to water.

I’m still seduced by the simplicity of my hypothesis…

To play Devil’s advocate: I don’t know of any mechanism by which the body can reclaim water from its urine, so it’s hard to see why keeping it in the bladder helps in any way.

Perhaps that’s not an instinct, but i think it is.

Peeing is good because it disposes of waste.

Being hydrated is good so we don’t die.

A balance is needed.

When you hear water running, that’s a good hint to stop economizing water. You’ll be drinking soon enough.

My thought is that predators could use a continuous trail of odoriferous excretions to locate groups of prey. If every one of the members of the group unload in the same spot then there is less of a clue as to their presence and which way they went. Yes, there will still be an odor trace where they walked but this is much harder to detect from a distance and will dissipate sooner than excreta.

A fair question – though they’ve been isolated so long that it might be a shared adaptation even if they don’t.

I doubt it is a learned response, as it is clearly present in infants.

To be fair I’ve had your thought more than once, but I cannot find a convincing way in which it would be adaptive. Removing everybody’s urine away from you might be beneficial, but only really if everyone else is doing it (the benefit is frequency dependent), and only at rather high population densities. Defecation is a much more toxic waste, and the sound of running water doesn’t inspire me to defecate…

Jacob

Jeffery Hodges

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She however had her own (like your Grandmum apparently) habit of farting in the Wal-Mart checkout line then -prior to the full effect – turning and hotly chiding, “Damn you JK !!”