Ask HN: Why did humans develop sense for sound waves but not other force fields?
Why did humans evolve to develop a sense to detect and act upon sound waves? Presuming we started from a single cell, how did it "know" that sound waves were even a thing to be interpreted and evolved towards? And if there is an innate tendency to develop senses, why did we not develop a way to detect and interpret magnetic fields? Or the other presumably infinite forces that exist and can convey information?
11 comments
Because they are large enough to be useful, simple to create, and ever–present.
No organism “knows” or “plans” the evolution of its species; it is random. Of course, if we were created then that’s another matter. In that case, our Creator knew that sound waves are large enough to be useful and that we would have a convenient atmosphere around at all times to create them in.
Magnetic fields, on the other hand, are tiny and difficult to manipulate. The same goes for gravity too, except more so. Gravity is 40 orders of magnitude weaker than the electroweak force. A small magnet can lift some paperclips, but to do the same with gravity you would have to dangle Venus above your desk. The strong force is even more useless.
There are no other forces. That’s all there is; electromagnetism, the weak force (which is really part of the electromagnetic force), the strong force, and gravity. Well, those four plus atoms bumping into each other, but atoms bump into each other using the electromagnetic force.
No organism “knows” or “plans” the evolution of its species; it is random. Of course, if we were created then that’s another matter. In that case, our Creator knew that sound waves are large enough to be useful and that we would have a convenient atmosphere around at all times to create them in.
Magnetic fields, on the other hand, are tiny and difficult to manipulate. The same goes for gravity too, except more so. Gravity is 40 orders of magnitude weaker than the electroweak force. A small magnet can lift some paperclips, but to do the same with gravity you would have to dangle Venus above your desk. The strong force is even more useless.
There are no other forces. That’s all there is; electromagnetism, the weak force (which is really part of the electromagnetic force), the strong force, and gravity. Well, those four plus atoms bumping into each other, but atoms bump into each other using the electromagnetic force.
I fully agree, but I can't resist nitpicking:
There is a detector of gravity in/near the earhttps://en.wikipedia.org/wiki/Vestibular_system It detects average gravity and is used for balance. But it (obviously) does not detect gravitational waves.
As the other comment said, some birds can detect magnetic field. And also some bacteria (archea?). They are also low sample rate detectors, enough to detect the direction (but IIRC not the strength).
There is a detector of gravity in/near the earhttps://en.wikipedia.org/wiki/Vestibular_system It detects average gravity and is used for balance. But it (obviously) does not detect gravitational waves.
As the other comment said, some birds can detect magnetic field. And also some bacteria (archea?). They are also low sample rate detectors, enough to detect the direction (but IIRC not the strength).
"a 2019 study found that magnetic fields do affect human alpha brain waves, but it is not known whether this results in any change in behaviour"
Magnetoreception - Wikipedia https://en.m.wikipedia.org/wiki/Magnetoreception
Magnetoreception - Wikipedia https://en.m.wikipedia.org/wiki/Magnetoreception
You’re right, I’d forgotten about that. The otoliths can detect the pull of the whole Earth, but gravity is so weak that anything smaller than a planet is undetectable.
Hearing didn't develop in humans. We inherited it. Trying to figure out why that was more useful than any other signal out there our ancestors could have developed the capability to perceive is inherently just spitballing. We can't possibly know. But at minimum, it is fairly simple to also create sound. As far as I know, hearing predates vocalization, but once a species learns the latter, the former becomes a lot more useful and is going to stick around.
Other animals can perceive magnetic fields, by the way. This is at least used by deep sea predators that live in the dark who sense the presence of prey by the electricity their bodies generate. Migratory birds use the earth's magnetic field to navigate long distances. It would appear neither of those use cases was enough of a killer app for our ancestors and thus didn't stick. Product market fit is all about filling the right niche at the right time. Plenty of great ideas don't make it that could have in other circumstances.
And, of course, as other comments pointed out, though we don't perceive magnetic fields, we do perceive electromagnetic waves. That's what light is.
Other animals can perceive magnetic fields, by the way. This is at least used by deep sea predators that live in the dark who sense the presence of prey by the electricity their bodies generate. Migratory birds use the earth's magnetic field to navigate long distances. It would appear neither of those use cases was enough of a killer app for our ancestors and thus didn't stick. Product market fit is all about filling the right niche at the right time. Plenty of great ideas don't make it that could have in other circumstances.
And, of course, as other comments pointed out, though we don't perceive magnetic fields, we do perceive electromagnetic waves. That's what light is.
Research has found some human brains can pick up on rotations of geomagnetic-strength fields as evidenced by drops in alpha wave power following stimulus: https://ve42.co/magneto
https://youtu.be/dg3pza4y2ws
https://youtu.be/dg3pza4y2ws
Photons are the carrier of the electromagnetic field. We “sense them”
via the photoelectric effect (i.e. photons activate electrons)…
We do not sense them via the magnetic force probably because it is useless for us (contrary to some species of birds IIRC).
We do not sense them via the magnetic force probably because it is useless for us (contrary to some species of birds IIRC).
A combination of cost-effectiveness and advantage
So there are two forces at work when it comes to evolution. The first is natural selection, which may start with random changes, where the structures that are beneficial tend to survive, hence there is a selection for them. The second is however that those random changes are restricted to changes that can physically happen, which depends on the laws of physics, and the structure itself.
The laws of physics themselves favor the selection for certain structures, and then those structures favor specific selections. It all keeps building up to more specific selections.
Thermodynamics itself always favors the creation of structures that dissipates free energy reservoirs, such as a star. Because heat death can't happen all at once, the system must move from one meta-stable state to another by dissipating structures feeding dissipating structures and so on. This is how entropy increases from minimum to maximum. There is however a minimum cost to maintaining a dissipating structure, so the feeding stops at structures that are barely left with enough potential energy to maintain themselves. The maintenance cost in fact increases the further away the structure is from the initial disequilibria, the star in this case. These bottom feeder structures are still thermodynamically favored since there is free energy left to do something, now however the selection changes. Now it's the structures that only create a minimum amount of entropy, structures that are thermodynamically efficient tend to survive, and dissipate another day, however slowly.
And here comes magic. It turns out that selection for thermodynamic efficiency is a selection for information processing, namely prediction. When a system interacts with it's environment it has a state, and that state is changed by the interaction. Some of that change correlates with past interactions, some with future ones. Turns out that how much of that state, or rather information (which is a physical thing like heat, because it needs a medium, and you can use the same statistical mechanics to describe it as well) correlates with future interactions is what thermodynamic efficiency is. This is called information thermodynamics, or the thermodynamics of prediction.
https://arxiv.org/abs/1203.3271
https://arxiv.org/abs/2009.04006
When there is enough state space for complex structures this thermodynamic pressure on bottom feeders is what creates information processing capabilities, including self-organizing structures like molecular machines that happen to approach 100% thermodynamic efficiency, and eventually things like DNS and nervous systems.
If you zoom out it's all lower entropy fighting it's way to higher entropy, creating things like stars, planets and us as a side effect. We are not the point, heat death is, it's just happens to be the case that you need structures like us for heat death to happen eventually. Not specifically us, but dissipating structures. We are bottom feeder dissipating structures, the worst of the bunch, but that also means that we get to think about it, which is cool. We get to predict the heat death. Or is it the heat death predicting itself? :-)
To answer the question we feel forces other than sound waves traveling in the medium we are in, and once you have a selection for prediction going on sooner or later you will wind up with organs that can aid creating computational models of the environment, to aid prediction, to aid thermodynamic efficiency, even at the cost of increasing complexity.
The laws of physics themselves favor the selection for certain structures, and then those structures favor specific selections. It all keeps building up to more specific selections.
Thermodynamics itself always favors the creation of structures that dissipates free energy reservoirs, such as a star. Because heat death can't happen all at once, the system must move from one meta-stable state to another by dissipating structures feeding dissipating structures and so on. This is how entropy increases from minimum to maximum. There is however a minimum cost to maintaining a dissipating structure, so the feeding stops at structures that are barely left with enough potential energy to maintain themselves. The maintenance cost in fact increases the further away the structure is from the initial disequilibria, the star in this case. These bottom feeder structures are still thermodynamically favored since there is free energy left to do something, now however the selection changes. Now it's the structures that only create a minimum amount of entropy, structures that are thermodynamically efficient tend to survive, and dissipate another day, however slowly.
And here comes magic. It turns out that selection for thermodynamic efficiency is a selection for information processing, namely prediction. When a system interacts with it's environment it has a state, and that state is changed by the interaction. Some of that change correlates with past interactions, some with future ones. Turns out that how much of that state, or rather information (which is a physical thing like heat, because it needs a medium, and you can use the same statistical mechanics to describe it as well) correlates with future interactions is what thermodynamic efficiency is. This is called information thermodynamics, or the thermodynamics of prediction.
https://arxiv.org/abs/1203.3271
https://arxiv.org/abs/2009.04006
When there is enough state space for complex structures this thermodynamic pressure on bottom feeders is what creates information processing capabilities, including self-organizing structures like molecular machines that happen to approach 100% thermodynamic efficiency, and eventually things like DNS and nervous systems.
If you zoom out it's all lower entropy fighting it's way to higher entropy, creating things like stars, planets and us as a side effect. We are not the point, heat death is, it's just happens to be the case that you need structures like us for heat death to happen eventually. Not specifically us, but dissipating structures. We are bottom feeder dissipating structures, the worst of the bunch, but that also means that we get to think about it, which is cool. We get to predict the heat death. Or is it the heat death predicting itself? :-)
To answer the question we feel forces other than sound waves traveling in the medium we are in, and once you have a selection for prediction going on sooner or later you will wind up with organs that can aid creating computational models of the environment, to aid prediction, to aid thermodynamic efficiency, even at the cost of increasing complexity.
What blows my mind about natural selection is sexual selection. The selection of individuals in a species. Individuals. Sure it's over extraordinary lengths of time. Most of the time. And in tons of species.
Then like floating trees carrying the first ancestors of a type to a new shore there's, again, evolution at the scale of the individual.
Mah brain explode.
Then like floating trees carrying the first ancestors of a type to a new shore there's, again, evolution at the scale of the individual.
Mah brain explode.
This is the best summary I read on the topic!