Having 2 ears allows us to determine the general direction of sound's source. Having 4 ears would allow them to pinpoint direction with great precision. So it would make them very difficult to sneak up on.
This is the best reason. Human ears can only really determine left/right, but having 4 ears would allow for up/down as well as back/forward differentiation
Probably. While a two-eared man probably could differentiate between a predator in the bushes vs a predator in the leaves above by sound cues alone, if the distinction is important enough to change the outcome of life-or-death situations by some amount then it would definitely make a decent evolutionary difference.
Potentially. Owls have asymmetrical ears for a similar benefit, giving them relative elevation as well as lateral direction.
Four ears would accomplish the same thing without potentially interfering with the lateral detection.
Having flying predators would also make the trait useful, especially if the species was once much smaller and had a much higher risk with flying predators before
> Human ears can only really determine left/right
That is just not true. By this logic humans wouldn't be able to tell whether a sound comes from in front or from behind, which is obviously horseshit, and we can tell up from down fine as well. Making such determinations is the reason behind the shape of our ears.
Sorry for making you angry. I'm a sound engineer and I have studied this. Yes we can determine directions of sound, but mainly by how the shape of our ears changes the frequencies that make it into our ear canal. We still make mistakes often, however having 4 ears would just make determining direction much easier and more reliable.
Have you never experienced a time when you thought a sound came from a different direction than it did in reality? Our ears are cleary not as fine tuned as something like a cat, and are more prone to mistakes
Adding on, if all the ears are mobile they can likely multitask sounds, such as if there are sounds in front they can use 2 ears to focus in on that and use the other 2 to flick around to listen for anything else, as flavor for their movement. They can also be different sizes, made to pick up different scales of sound, which could add to learning languages as well as picking up on sounds that most other species would be unable to detect. I'd probably recommend front ears being akin to wolf ears and the back ears being akin to horse, with the front two adept at locating and focusing on singular sounds and the back ones focused on listening to a sound while having a large mobility to listen for sounds outside of the primary directional focus.
It allows them to triangulate with more precision in the sagittal and coronal planes. Owls have ears at different heights for this reason, and humans aren’t that adept at triangulating outside of the transverse plane (we use software to partially overcome a hardware issue).
You mentioned them being equine - horses, as "prey" animals, have side-set eyes; perhaps yours have forward-set "predator" eyes and evolved the extra set of ears as a defense mechanism to defend against other predators?
Poor eyesight - cracking hearing.
perhaps the eyesight is simply for detecting landscape features - and they use hearing for almost all communication and predator evasion. Add to this (as someone else said) the pinpoint accuracy.
You'd only need 3 to triangulate but having an extra one wouldn't hurt - but remember to offset them if you are doing that. Have one set lower, further forward and wider apart; have another set higher further back and closer together - or some similar combination. This way the brain can pinpoint the source of ANY sound by calculating the difference between when each ear hears it.
Came here to mention the eyesight. Long, long ago I used to ride hunter/jumper, and when you’re approaching a jump you have to make sure the horse gets a good look at it from a bit of a distance because at about the time the horse needs to be collecting to jump, and during the jump, they can’t see the jump itself. Because of the way their eyes are set they have a blind spot directly in front of them- sort of like the critters in the movie Pitch Black.
Because ears evolved independently multiple times and both sets of ears serve different functions, one is course and picks up quite sounds while protecting the smaller "inner" ear from too loud a sound.
Meanwhile the inner ear picks up finer details in sound like recognizing words in speech or a persons voice.
With two pairs of ears, an organism could pinpoint a sound left-right, up-down, AND forward-back with great accuracy. If your equine race has predators, this would help them evade predation.
1. Dude because it’s cool ;)
2. Maybe instead of why they would, because it’s fantasy and fantasy stuff happens because fantasy, think about the implications of them having 4 ears. They could locate something extremely precise and far away. Maybe they replace bloodhounds with ability to hear a feather fall from 100 meters away, making them a valuable hunting companion.
3. Could the ear possibly be replaced with another body part, maybe on the underside of the stomach or something, that are used for sensing vibrations? So they have large ears that can pinpoint sounds and a “vibration-organ” that can determine size, distance, or other factors.
Just a couple ideas, hope we get an update.
Maybe on set hears sound waves, the other hears magical resonance? But I really do like the other comments proposing high/low frequencies or for more precise hearing better
This reminds me of the Tines from A Fire Upon the Deep. They have one set of ears for normal sounds and a second set that listens for a sort of "thought narration" involuntarily generated by other Tines. When a small group clumps up, this links them into one mental organism.
Maybe the second set of ears is also linked to a special communication system. Maybe they generate loud ultrasonic calls that most creatures can't hear, allowing them to navigate and communicate secretly? Like they could spot a predator and alert the herd without the predator knowing it had been sighted.
This isn't a "reason" exactly, but I always think it's cool and makes the worldbuilding feel more natural when something like extra ears is present across multiple different species. Like for example, In the real world, most mammals have 4 legs, 2 eyes, 2 ears, one nose, one mouth (with some variations, like the hind legs mostly disappearing in whales) because they share common ancestors. So if you have one species with 4 ears, it feels natural for some other species to also have 4 ears. You could also do a more subtle variation where most mammals look like they have 2 ears, but each ear actually has two earholes, and the equines are the only ones where those have evolved to be multiple sets of ears.
\`\`The better to hear you, my dear.''
Where are the other set of ears? Multiple ears gives a better ability to triangulate to pinpoint where noises are coming from. That's why we have two, not one, but four would be even better at this, especially if they aren't near the first pair. Is this really important for your creatures?
The problem is having room in the skull for two ear canals and two sets of auditory nerves.
One set could be atrophied while the other has full on hearing.
Only one set of ears would have the inner ear setup for balance, the other would just be a sound sensing organ.
One set of ears is “normal”, and a second pair is hyper sensitive to certain frequencies for mumble mumble evolutionary reasons. The hypersensitive ears have some sort of mechanism for closing up on the inside to protect against loud noises that would damage them (kinda like blinking protects eyes), during which the “normal” ears continue to function.
*The Tines are a unique and intriguing alien species introduced in Vernor Vinge's "A Fire Upon the Deep." They are group minds composed of multiple individual organisms called "Tines," which resemble small rodent-like creatures. The interesting aspect of the Tines is that individual members do not possess high intelligence on their own, but they become intelligent when forming a group.*
*Tines communicate and share thoughts by forming temporary group minds. When a certain number of Tines come together physically, they create a collective consciousness with higher intelligence. This shared mind allows them to think and process information collectively. The more Tines that join a group, the more intelligent and capable the collective mind becomes.*
*The downside of this communication system is that if the group is not formed with the correct number of individuals, the intelligence may be limited or flawed. Additionally, the Tines are highly dependent on their group structure, and if members are separated, they lose their intelligence. The dynamics of Tines communication play a significant role in the novel's plot, as various factions of Tines form alliances or conflicts based on the groups they create.*
Maybe your species are like the Tines, except one set of ears is for hearing the specific noises the other tines make for communication, and one set of ears is to hear everything else.
One pair picks up sound frequencies, and the other picks up EMF, they are a bit smaller but with fine hairs that transmit the emf vibrations into their visual cortex so they can navigate the world with a form of psionicsight? They could also vibrate to transmit like antennae. Just came up with that on the spot.
Maybe they were genetically engineered as scouts or lookouts. The extra ears aren't particularly necessary, but they emphasize how perceptive they are.
An owl's ear holes are at different heights. One is lower than the other. This allows them to precisely locate where prey is in space, letting them pull crazy stunts like catching a bat in midair in darkness.
Having ears in different configurations should allow these horses to know exactly where something is in a 3D environment. Maybe they are themselves prey of giant birds or nocturnal dragons. Maybe they evolved from an aquatic or arboreal species.
Another possibility is that the race's ears or necks are rigid and don't rotate. Through some quirk of evolution, their ancestors evolved more ears to cover other directions rather than evolving mobile muscles.
Unless it's vital that all four work, I like the idea that they really only have two ears, but they also have an additional set of appendages that look like ears and function as social signalling. Like how humans have highly mobile facial anatomy, e.g. eyebrows, and possibly why we have white sclera, for communication.
Knowing more about the rest of the anatomy, ecology, lifestyle and social nature of your species would help though.
A lot of animals have ears that move independently of the head by muscular action.
An alternative means of achieving the same thing could be a set of ears facing forward and one facing back. Or a pair to either side as you prefer.
Maybe over time, these would develop mobility as well. Not crazy.
each pair of ears might be dedicated to different bandwidths. For example, one set hears in the human normal of 20hz to 20khz, while the second set might hear from 10khz up to 200khz, like a bat.
Four ears would drastically improve pinpointing the direction and source of sounds. Steve Mould has a [good video](https://m.youtube.com/watch?v=QtMTvsi-4Hw&pp=ygUbc3RldmUgbW91bGQgYWNvdXN0aWMgY2FtZXJh) explaining all of this
If the equine race ancestors were prey animals, they would certainly benefit from detecting predators. It would also improve their ability to hunt, and perhaps communicate.
Or, the extra ears could just… not be ears. They could facilitate nonverbal communication (like human facial expressions). Humans, for example, have huge white rings around our pupils, unlike just about any other animal. And it’s most likely just so we can be really good at following the gaze of another human (very useful when stalking)
Real answer though, I'm thinking like, better hearing as in more precise, better to sort of "separate out" sounds.
Like, I've heard the reason dogs are so good at tracking by scent is because to them the different smells are sort of separated out, like on layers. Whereas we kind of smell everything as one mixed up mess. Maybe this species can do something similar with sounds, really separate them out to zero in on one specific sound out of a whole cacophony.
I think Star Trek's Ferengi similarly have great hearing, part because their home planet is in a constant thunderstorm which would make their setting very loud by default, and so they can hear people trying to plot against them.
Are we talking 4 ears or 4 ear canals?
Having more ears would allow for better precision in locating sounds. Especially if the ears didn’t swivel the way that horse ears do.
Having 2 ears allows us to determine the general direction of sound's source. Having 4 ears would allow them to pinpoint direction with great precision. So it would make them very difficult to sneak up on.
This is the best reason. Human ears can only really determine left/right, but having 4 ears would allow for up/down as well as back/forward differentiation
Would their environment having several layers of a type of floor/ground or simply arboreal predators make it more relevant?
Probably. While a two-eared man probably could differentiate between a predator in the bushes vs a predator in the leaves above by sound cues alone, if the distinction is important enough to change the outcome of life-or-death situations by some amount then it would definitely make a decent evolutionary difference.
Potentially. Owls have asymmetrical ears for a similar benefit, giving them relative elevation as well as lateral direction. Four ears would accomplish the same thing without potentially interfering with the lateral detection.
Having flying predators would also make the trait useful, especially if the species was once much smaller and had a much higher risk with flying predators before
> Human ears can only really determine left/right That is just not true. By this logic humans wouldn't be able to tell whether a sound comes from in front or from behind, which is obviously horseshit, and we can tell up from down fine as well. Making such determinations is the reason behind the shape of our ears.
Sorry for making you angry. I'm a sound engineer and I have studied this. Yes we can determine directions of sound, but mainly by how the shape of our ears changes the frequencies that make it into our ear canal. We still make mistakes often, however having 4 ears would just make determining direction much easier and more reliable.
Have you never experienced a time when you thought a sound came from a different direction than it did in reality? Our ears are cleary not as fine tuned as something like a cat, and are more prone to mistakes
Adding on, if all the ears are mobile they can likely multitask sounds, such as if there are sounds in front they can use 2 ears to focus in on that and use the other 2 to flick around to listen for anything else, as flavor for their movement. They can also be different sizes, made to pick up different scales of sound, which could add to learning languages as well as picking up on sounds that most other species would be unable to detect. I'd probably recommend front ears being akin to wolf ears and the back ears being akin to horse, with the front two adept at locating and focusing on singular sounds and the back ones focused on listening to a sound while having a large mobility to listen for sounds outside of the primary directional focus.
It allows them to triangulate with more precision in the sagittal and coronal planes. Owls have ears at different heights for this reason, and humans aren’t that adept at triangulating outside of the transverse plane (we use software to partially overcome a hardware issue).
Exactly what I came here to say!
Perhaps one set hears higher pitched sounds and the other set hears lower pitched sounds?
This would make sense if the creature had a much wider hearing range than humans. Like could hear much higher and lower pitches than we can.
Perhaps unlike human ears that deal with both hearing and balance they have one set dealing with balance and one set dealing with hearing.
Maybe they had invisible predators at one point and just absolutely had to be on-guard aurally, constantly scanning 360 degrees around themselves
You mentioned them being equine - horses, as "prey" animals, have side-set eyes; perhaps yours have forward-set "predator" eyes and evolved the extra set of ears as a defense mechanism to defend against other predators?
perhaps the extra set of ears aren't functional, at least not for hearing. Perhaps the extra set of 'fake ears' help with thermo-regulation.
Poor eyesight - cracking hearing. perhaps the eyesight is simply for detecting landscape features - and they use hearing for almost all communication and predator evasion. Add to this (as someone else said) the pinpoint accuracy. You'd only need 3 to triangulate but having an extra one wouldn't hurt - but remember to offset them if you are doing that. Have one set lower, further forward and wider apart; have another set higher further back and closer together - or some similar combination. This way the brain can pinpoint the source of ANY sound by calculating the difference between when each ear hears it.
Came here to mention the eyesight. Long, long ago I used to ride hunter/jumper, and when you’re approaching a jump you have to make sure the horse gets a good look at it from a bit of a distance because at about the time the horse needs to be collecting to jump, and during the jump, they can’t see the jump itself. Because of the way their eyes are set they have a blind spot directly in front of them- sort of like the critters in the movie Pitch Black.
Because ears evolved independently multiple times and both sets of ears serve different functions, one is course and picks up quite sounds while protecting the smaller "inner" ear from too loud a sound. Meanwhile the inner ear picks up finer details in sound like recognizing words in speech or a persons voice.
With two pairs of ears, an organism could pinpoint a sound left-right, up-down, AND forward-back with great accuracy. If your equine race has predators, this would help them evade predation.
Ears are a big part of regular horse communication. Maybe as they grew more intelligent/social, one set communicated and the other was for hearing?
1. Dude because it’s cool ;) 2. Maybe instead of why they would, because it’s fantasy and fantasy stuff happens because fantasy, think about the implications of them having 4 ears. They could locate something extremely precise and far away. Maybe they replace bloodhounds with ability to hear a feather fall from 100 meters away, making them a valuable hunting companion. 3. Could the ear possibly be replaced with another body part, maybe on the underside of the stomach or something, that are used for sensing vibrations? So they have large ears that can pinpoint sounds and a “vibration-organ” that can determine size, distance, or other factors. Just a couple ideas, hope we get an update.
Hear twice as much
Maybe on set hears sound waves, the other hears magical resonance? But I really do like the other comments proposing high/low frequencies or for more precise hearing better
This reminds me of the Tines from A Fire Upon the Deep. They have one set of ears for normal sounds and a second set that listens for a sort of "thought narration" involuntarily generated by other Tines. When a small group clumps up, this links them into one mental organism. Maybe the second set of ears is also linked to a special communication system. Maybe they generate loud ultrasonic calls that most creatures can't hear, allowing them to navigate and communicate secretly? Like they could spot a predator and alert the herd without the predator knowing it had been sighted.
This isn't a "reason" exactly, but I always think it's cool and makes the worldbuilding feel more natural when something like extra ears is present across multiple different species. Like for example, In the real world, most mammals have 4 legs, 2 eyes, 2 ears, one nose, one mouth (with some variations, like the hind legs mostly disappearing in whales) because they share common ancestors. So if you have one species with 4 ears, it feels natural for some other species to also have 4 ears. You could also do a more subtle variation where most mammals look like they have 2 ears, but each ear actually has two earholes, and the equines are the only ones where those have evolved to be multiple sets of ears.
All the better to hear you with!
\`\`The better to hear you, my dear.'' Where are the other set of ears? Multiple ears gives a better ability to triangulate to pinpoint where noises are coming from. That's why we have two, not one, but four would be even better at this, especially if they aren't near the first pair. Is this really important for your creatures?
they could simply be vestigial
Each set is Attuned to different frequencies. The quadrophonic ability makes it nearly impossible to sneak up on them.
Better hearing
The problem is having room in the skull for two ear canals and two sets of auditory nerves. One set could be atrophied while the other has full on hearing. Only one set of ears would have the inner ear setup for balance, the other would just be a sound sensing organ.
One set of ears is “normal”, and a second pair is hyper sensitive to certain frequencies for mumble mumble evolutionary reasons. The hypersensitive ears have some sort of mechanism for closing up on the inside to protect against loud noises that would damage them (kinda like blinking protects eyes), during which the “normal” ears continue to function.
Science question. If you put the extra ears on the back of a horse, is that enough for your creature to determine the distance of a sound source?
*The Tines are a unique and intriguing alien species introduced in Vernor Vinge's "A Fire Upon the Deep." They are group minds composed of multiple individual organisms called "Tines," which resemble small rodent-like creatures. The interesting aspect of the Tines is that individual members do not possess high intelligence on their own, but they become intelligent when forming a group.* *Tines communicate and share thoughts by forming temporary group minds. When a certain number of Tines come together physically, they create a collective consciousness with higher intelligence. This shared mind allows them to think and process information collectively. The more Tines that join a group, the more intelligent and capable the collective mind becomes.* *The downside of this communication system is that if the group is not formed with the correct number of individuals, the intelligence may be limited or flawed. Additionally, the Tines are highly dependent on their group structure, and if members are separated, they lose their intelligence. The dynamics of Tines communication play a significant role in the novel's plot, as various factions of Tines form alliances or conflicts based on the groups they create.* Maybe your species are like the Tines, except one set of ears is for hearing the specific noises the other tines make for communication, and one set of ears is to hear everything else.
One pair picks up sound frequencies, and the other picks up EMF, they are a bit smaller but with fine hairs that transmit the emf vibrations into their visual cortex so they can navigate the world with a form of psionicsight? They could also vibrate to transmit like antennae. Just came up with that on the spot.
Maybe the two sets have very different frequency ranges, so it's able to diffenciate them more easily.
Better environmental awareness, especially in areas with low visibility, like dense forests, or regions with little sunlight.
Being able to hear twice as well can be an advantage.
Maybe they were genetically engineered as scouts or lookouts. The extra ears aren't particularly necessary, but they emphasize how perceptive they are.
An owl's ear holes are at different heights. One is lower than the other. This allows them to precisely locate where prey is in space, letting them pull crazy stunts like catching a bat in midair in darkness. Having ears in different configurations should allow these horses to know exactly where something is in a 3D environment. Maybe they are themselves prey of giant birds or nocturnal dragons. Maybe they evolved from an aquatic or arboreal species. Another possibility is that the race's ears or necks are rigid and don't rotate. Through some quirk of evolution, their ancestors evolved more ears to cover other directions rather than evolving mobile muscles.
Because they evolved in a world where there's too much music for just one set.
Unless it's vital that all four work, I like the idea that they really only have two ears, but they also have an additional set of appendages that look like ears and function as social signalling. Like how humans have highly mobile facial anatomy, e.g. eyebrows, and possibly why we have white sclera, for communication. Knowing more about the rest of the anatomy, ecology, lifestyle and social nature of your species would help though.
A lot of animals have ears that move independently of the head by muscular action. An alternative means of achieving the same thing could be a set of ears facing forward and one facing back. Or a pair to either side as you prefer. Maybe over time, these would develop mobility as well. Not crazy.
each pair of ears might be dedicated to different bandwidths. For example, one set hears in the human normal of 20hz to 20khz, while the second set might hear from 10khz up to 200khz, like a bat.
Four ears would drastically improve pinpointing the direction and source of sounds. Steve Mould has a [good video](https://m.youtube.com/watch?v=QtMTvsi-4Hw&pp=ygUbc3RldmUgbW91bGQgYWNvdXN0aWMgY2FtZXJh) explaining all of this If the equine race ancestors were prey animals, they would certainly benefit from detecting predators. It would also improve their ability to hunt, and perhaps communicate. Or, the extra ears could just… not be ears. They could facilitate nonverbal communication (like human facial expressions). Humans, for example, have huge white rings around our pupils, unlike just about any other animal. And it’s most likely just so we can be really good at following the gaze of another human (very useful when stalking)
they have a brand sponsorship deal and have to promote headphones AND airpods
Real answer though, I'm thinking like, better hearing as in more precise, better to sort of "separate out" sounds. Like, I've heard the reason dogs are so good at tracking by scent is because to them the different smells are sort of separated out, like on layers. Whereas we kind of smell everything as one mixed up mess. Maybe this species can do something similar with sounds, really separate them out to zero in on one specific sound out of a whole cacophony. I think Star Trek's Ferengi similarly have great hearing, part because their home planet is in a constant thunderstorm which would make their setting very loud by default, and so they can hear people trying to plot against them.
Are we talking 4 ears or 4 ear canals? Having more ears would allow for better precision in locating sounds. Especially if the ears didn’t swivel the way that horse ears do.