Why can't we close our ears?

Hello All,

I’ve often wished I could have evolved so I could close my ears (without the obvious use off fingers or hands). It would be really useful in all sorts of situations, public transport, noisy neighbours, office meetings, etc. Plus it would protect our delicate ear drums?

I wonder why we didn’t?

I wonder if any animal can?

All kinds of things could be useful to us if we were suitably equipped, but we are not. Utility is a reason for adaptations persisting once they arise, not a reason for them arising in the first place.

Evolution doesn’t provide everything we might need - it merely lets us keep what has happened, and is useful.

Okay, why haven’t we at least invented a Cone of (Temporary) Deafness? I use 32db-rated earplugs all the time, and while they reduce ambient noise, I can still follow a conversation at ordinary volume. (I assume this is because they don’t actually block out 32 db of noise, not because I have super hearing.)

If we HAVE invented a Cone of (Temporary) Deafness, could you please direct me to it?

Right here.

These types of situations have been largely absent for most of human evolution.

The real question is how the noise of public transportation and office meetings are interfering with reproduction. I think we need details! :slight_smile:

Actually, our ears have 3 different mechanisms for dealing with how loud the ambient sound level is and adjusting to them. One is nerves inhibiting neighbors, which helps bring signal above noise regardless of the sound level. Another is the set of muscles that tighten our eardrums during loud noises (ever notice how your often hear and feel a scrunching thing going on in your ears when the loud noise stops, or the damn guitarist turns down? That’s the muscles relaxing.) There’s a third which I can’t remember at present but is probably covered nicely in wikipedia.

Our ears can handle an amazing 100 decibels or more in range from the quietest to the loudest sounds. That’s 10 orders of magnitude, in terms of sound pressure! (Square that, to get it in terms of energy levels.) It’s astonishing.

So, you want yet another adaptation to handle an even wider range? For what? What evolutionary environment would require an even higher range? 100dB SPL (what they used to call the “pain threshold” but what we now call a “not terribly loud band”, reserving that for 110 dB SPL) is really quite loud. Unless we’re all living underneath 747’s constantly taking off, it’s really quite enough.

Humans actually have a muscle in the inner ear which dampens loud sounds.
ETA: Scooped by Learjeff.

I get a little syringe and fill it with petroleum jelly and shoot that into my ears and it’s pretty quiet for days.

Most likely, we don’t really want to. Sound can get our attention because it isn’t focused like vision. Not being able to block it is a useful trait that helps us understand what is going on where we can’t see.

All of the people who could close their ears were eaten. Brain scans show that, even in deep sleep the areas of your brain that process hearing continue to function as if awake. This allows us to hear an approaching mountail lion as we sleep…or, more benignly, an alarm clock.
Evolution has weeded out the selectively deaf. They selected poorly.

How is conscious control of what you hear any different for evolutionary fitness than conscious control of what you see by shutting your eyelids? Humans are more visual than auditory, but conscious control of sight doesn’t seem to have hurt us.

As others have said, evolution doesn’t work that way; it doesn’t just create desirable things if there wasn’t a mutation for it in the first place. Sure, we’d be better off if we had wings, but if nobody’s born with wings, and thereby has an increased ability to reproduce, it’s not gonna happen.

Non-biologist WAG: eyes are more delicate/exposed than ears and need more protective covering?

The sensitive parts of your auditory equipment are tucked safely away in a narrow hole in your skull and shielded by semi-rigid folds of skin and cartilage (which also act as sound amplifiers). Additional shielding wouldn’t add much protection.

But much of the most delicate material in your ocular equipment is right out there on the surface of your face, gathering data while directly exposed to dust and smoke and flying insects and clumsy fingers and who knows what all. Having retractable shields for the sensors is pretty important in that case.

It’s not so much about controlling what you see (how often during an average day do you deliberately shut your eyes, after all?) as about controlling what potentially damaging substances come into contact with your eyes.

About 50% of people develop the ability after getting married. The rest don’t stay married.

Google “ipod pedestrian deaths” to get a view of the Darwinian effects of selective environmental deafness. Hearing is our primary always-on alert system - we can’t turn it off because there has been no selective pressure to evolve that ability, and it has almost certainly been selected against.

Si

Ah! That also answers another of my questions. Given that sunlight falling on earth gives approx 1.4Kw/m2 and we all evolved in Africa, why didn’t we evolve to have solar powered skin, it would save chasing antelope :slight_smile:

Yeah, but it really sucks not being able to run away from nocturnal hunters. Evolution in action.

Si

This is very true

I’ve noisy neighbours in the flat above me and have resorted to wearing ear plugs when it’s particulary bad. And it is surprising how ‘clumsy’ you become when you can’t hear. It’s so much easier to accidentally break stuff or knock things over, and even trip over, you become very isolated from your enviroment.

I thought it’s because ear plugs don’t block out much of the frequencies used for voice, but block other frequencies instead. At least, I think that’s what gun earplugs do.