I’ve always found this semantic argument somewhat silly as being blind or deaf is an obvious disadvantage in natural contexts, but one of the more compelling ideas here is that the fitness boundary isn’t fixed. It would probably be a fitness advantage if I could sense electromagnetic fields, but no one would describe me as disabled for not being able to sense these fields—unless, perhaps, everyone else could.

So what we consider to be a disability does seem to be a function of what we consider to be normal.

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kazinator a day ago | parent | next [-]

If it were a fitness advantage if you could sense electromagnetic fields, then why have you evolved over billions of years to get where you are, without it?

But wait, you do sense electromagnetic fields in the 380 to 750 nm wavelength range, and remarkably well, to great profit.

The only fitness advantage that matters for evolution is whatever gets you to pass down your genes, versus someone else not passing down theirs. If sensing low-frequency electromagnetism, or static magnetic fields, were advantageous in the context of everything else that you are, for passing down your genes, you would have it by now.

Migratory birds can sense the Earth's magnetic field for navigation; if you needed to migrate thousands of kilometers every year (due to lacking other advantages to make that unnecessary), you might evolve that.

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zmgsabst a day ago | parent [-]

Evolution is highly path dependent and stochastic, so I’m not sure your logic follows.

Eg, the laryngeal nerve in giraffes is ridiculous — but having gone down that path before their current form, there’s little way to fix it. They’re now stuck in a local optima of long necks (good) with poor wiring (bad).

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kazinator 8 hours ago | parent | next [-]

Yes it it path dependent; my example alludes to it. Birds benefit from being able to sense the magnetic field for navigation precisely because they evolved the ability to fly, and the endurance to do that over long distances. In that context, not losing your bearing is a fitness advantage.

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UltraSane a day ago | parent | prev [-]

Vision has evolved numerous times, with estimates suggesting eyes or light-sensitive spots have appeared independently at least 40 to 65 times, possibly even 100 times, across different animal lineages.

Hearing has evolved numerous times independently, at least six times in major vertebrate groups (mammals, lizards, frogs, birds, crocodiles, turtles) for airborne sound and at least 19-20 times in insects

Vision and hearing have evolved so many times because they give an absolutely huge survival advantage.

	▲	avadodin 19 hours ago \| parent [-]
		Do you have sources for these claims? To my knowledge, photosensitivity has arisen a few times independently and eyes again a few times from shared photosensitive receptors in animalia but I'm fairly sure hearing in the groups you mention is a tetrapod synapomorphy.

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rdtsc 13 hours ago | parent | prev | next [-]

> if I could sense electromagnetic fields, but no one would describe me as disabled for not being able to sense these fields—unless, perhaps, everyone else could.

Light is EM fields. A possible scenario is a battle at night with others having night vision equipment and you don’t. You can absolutely be described as disabled or being at a significant disadvantage.

Because, like you say, what we consider normal in that scenario is to have a proper night vision equipment.

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suddenlybananas a day ago | parent | prev [-]

>So what we consider to be a disability does seem to be a function of what we consider to be normal.

Obviously? How could it be based on anything else? People are just much more uncomfortable with making normative statements than they used to be.

	▲	lurk2 a day ago \| parent [-]
		> How could it be based on anything else? The point is that the capability is measurable but the capabilities we consider to be essential are based on normalcy and thus effectively arbitrary. Eugenicists make the argument that evolution demonstrates that the classification is not arbitrary because deafness and blindness confer measurable fitness disadvantages, but they don’t actually bridge the gap of deriving an ought from an is. > Obviously? If the answers to these problems are obvious to you, perhaps you’d consider writing a book instead of participating in a discussion forum. I would encourage you to review the site guidelines.