It's a typo or the author forget how outsiders work. The descriptions in the Planar Handbook state unambiguously that the outsider races presented therein are mortal creatures that need nourishment, age and reproduce like other mortal creatures.
Races presented in the planar handbook:
Aasimars, Bariaurs, Buommans, Mephlings, Neraphim, Shadowwyfts, Spikers, Tieflings, Wildren.
Race TYPES presented (in order):
Outsider (native), Outsider (EP), Humanoid (EP), Humanoid (EP), Outsider (EP), Outsider (EP), Humanoid (EP), Outsider (native), Outsider (EP).
Please note that I am saying EP as shorthand for Extraplanar, and I am giving it in the case that all of these creatures are on the material plane.
Beyond that; humanoids need to nourishment, age and reproduce, native outsiders too. The true outsiders may be required to do all of that, but it would be an exception - specifically noted in their race write up - from the rule that states:
"Outsiders breathe, but do not need to eat or sleep (although they can do so if they wish). Native outsiders breathe, eat, and sleep." [From the SRD and PFSRD.]
I do have a quick question, would you have such a problem if the word 'native' was replaced with 'material'? Just wondering.
Otherwise it's not really balanced to have pure outsiders as PC races (at least not without an LA +1 at the very least) due to their blanket spell immunity, lack of need to eat/sleep and inability to be raised or resurrected if killed (barring the spell "revive outsider" which, IIRC, did not exist at the time the PlH was published).
"Blanket spell immunity." Where are they getting that? Irrelevant. The LA or immunity or any such issues are a balancing issue and have nothing to do with the 'native subtype doesn't make sense' conversation. Also at the time the PHB was released, neither did these races in the Planar Handbook (it came after). But once again that is irrelevant.
Celestial and fiendish creatures are planar counterparts of material creatures.
I'm going to pause here for a moment. Celestial and fiendish creatures are TEMPLATES applied to other creatures. Just as the half-dragon template can be applied to other creatures. I don't think it is a fair comparison to discuss them in conjunction with all outsiders on that basis. That is why I asked for EXAMPLES, and specifically excluded those templated creatures.
Okay, unpausing..
They are not material creatures that have adapted to the outer planes.
Well, it is a quick rebuild template in PF. So it is hard to say where the creature started. But you are right, it is unlikely that it adapted to the outer planes in the traditional sense I gave - generationally. With that said, it does specifically apply a template that adapts it to the outer planes. Just the same if I had originally talked about people living on an acid planet eventually developing acid immunity, but then you bring up black half-dragons as a counter-argument.
Both templates are inherited templates, meaning the creatures are born with it, it can't be applied to an existing material creature (outside special circumstances).
I think you are wrong here in two ways. First, where does it show on the below link that they are BORN with this template? Second, the link specifically says 'rebuild rules' implying that it is rebuilding a creature that is not already a celestial/fiend. So that discounts 'can't be applied to existing material creature'.
http://www.d20pfsrd.com/bestiary/monster-listings/templates/celestial-creature-cr-special
While some planar creatures might be naturalized, most of them seem to have been born from the planes or created from scratch to populate them.
Examples? Celestial dogs? Teiflings? Mephlings? Who are you talking about?
The extraplanar subtype simply didn't exist until 3.5 edition.
Also irrelevant, given what the subtype means.
Before then, all creatures from outer planes were stated as outsiders, even if they otherwise resembled animals, humanoids, etc.
Correct. We agree. After the EP subtype was introduced too. Extraplanar doesn't belong to outsiders, it belongs to ALL creatures that are not on their home plane. By all rights it shouldn't be a subtype, it should be a status effect like paralysis. A status effect meaning the creature can be banished back to their home plane. A status effect that can't be removed by magic, ever.
Whereas 3.5 open the door for extraplanar creatures of other types and made these the default form of life on the outer planes (e.g. the celestial and fiendish templates).
I'm once again going to ask for examples that are not those templates. But if you are talking about humanoids living on the planes, anyone can do that, it doesn't make them outsiders so I don't see your point exactly.
However, the outsider type is still used for any kind of creature from the outer planes (aside from celestial, entropic, fiendish and resolute creatures), even if another type would be equally appropriate.
Such as? When is another type more appropriate. I'm not accepting 'equally', I demand MORE.
Outsiders have absolutely nothing in common with one another besides being extraplanar and immune to spells that don't affect outsiders.
Dragons have nothing in common with one another besides being able to breathe fire and immune to spells that don't affect dragons. And?
Humanoids have nothing in common with one another besides being able to die, reproduce, eat, sleep, and immune to spells that don't affect humanoids. So.
I'm just saying that argument doesn't hold a lot of weight.
Just take any creature that, if it were native to the material plane, would be one of the standard types and make it into an outsider.
Correct.
There's really no reason why outsiders can't have the same variety of types as material creatures can with the associated changes to hit dice, skills, traits, etc except for the arbitrary "anything not from the material plane is automatically an outsider, except for all these numerous exceptions."
That is not what defines an outsider. Also, just because you become naturalized doesn't mean you become an outsider either. It is something you have or you don't. If the type was a dragon, living on a place called 'dragon-place' and a bunch of people moved there and kept to themselves they wouldn't suddenly become dragons, but they may become naturalized enough to not be considered foreigners to the dragons. Not really the same thing.
The native subtype makes three unrelated changes to the outsider type: native outsiders are native to the material plane (which can also be accomplished by removing the extraplanar subtype),
I'm stopping right here. NO IT ISN'T. Native is not the other end of the extraplanar scale. They are unrelated things. It is like saying 'humans are native to X nation (which can also be accomplished by making them paralyzed). It is nonsense.
native outsiders must eat and sleep, and native outsiders can be raised and resurrected. The same result can be achieved by giving a non-outsider type the quality "vulnerability to effects that specifically target outsiders."
What? Are you saying that native outsiders shouldn't be, because they could easily be 'humanoids (outsider)' or something? That is basically what they are already.
There are several types of native outsiders with dramatically different origins: planetouched are the descendants (often many, many generations later) of couplings between mortals and celestials, fiends or genies, while tritons are outsiders who emigrated to the material plane and somehow developed the native subtype. If, as tritons indicate, outsiders can gain the native subtype simply by living and reproducing on the material plane for centuries (without interbreeding with humanoids), then it stands to reason that animals, humanoids, etc can become outsiders by living and reproducing on the outer planes for centuries (without interbreeding with outsiders).
Premise A. Tritons don't reproduce with human[oid]s.
Premise B. Tritons became native outsiders sheerly through naturalization.
Conclusion: If Tritons can do it to become native humanoids, why can't other creatures do it to become outsiders.
Here's what's wrong with that? Your conclusion isn't drawn from your premises. And your premises are faulty. According to the MM "Tritons are thought to originate from the Elemental Plane of Water." But how distantly is unclear. Why they are not there anymore is unclear. For all is known there may have been a previous race of pure tritons that came from the elemental plane of water, but is unknown. For that matter it could be that they DID breed with humanoids (my guess would be merfolk, if true) and became native outsiders that way. But either way, it is unclear and unknown.
Assuming they did become native outsiders through nothing more than naturalization (moving to the material plane and staying there long enough to breed true as native outsiders) isn't much better. The description says it was a long time ago. Presumably the first generation (maybe several) were Outsider (water, EP) and then eventually the EP dropped. Then some time later they became so unrelated to the elemental plane of water that they simply became (native).
And finally, just because we know creatures can go from outsider to native outsider over long periods of time does not mean the opposite is true. Going back to dragons, unless you are born with dragon in you, you are never considered dragon-blooded. They are unrelated things. The outsider is called that because of where it came from, but it doesn't apply universally to all creatures that live there. Living there is not enough of an indicator.
You have to be made of the stuff. Just like living in the elemental planes doesn't make you an elemental, you have to physically be living fire/water/whatever. If a fire elemental was able to somehow breed with a human, and make a Elemental (fire, native) [in 3.5] or Outsider (elemental, fire, native) [in PF] somehow. It still wouldn't change the fact for those humans living in the city of brass, if they kept to themselves and stayed exactly as they were, would remain Humanoid (human). Their type wouldn't spontaneously include Outsider stuff in it. They wouldn't cease being carbon based lifeforms and become energy based. It doesn't work like that. The naturalization I talk about is the EP tag, that you can get fairly easily by being born in a place and your parents and theirs and so on. The native subtype denotes being made of the material plane, not being simply born there.
The child-devil (from my previous post) would have to be physically made of material plane in a way that their devil parent/s generally are incapable of doing. Over time through the generations the devils may be able to incorporate enough material matter into their physiology in order to have a native outside devil baby, but it is unlikely, lengthy, and hard to do. Requires commitment of species and generations, not on a personal scale.
If, as the planetouched indicate, all the descendants of an outsider and a mortal are native outsiders regardless of how many generations removed, then the material plane should be filled with native outsiders.
Why is that? It would be like saying that the material plane should be filled with humans, or half-elves, or half-dragons, or any race simply because they exist. The planetouched description even says, "The effects of having a supernatural being in one's heritage last for many generations." But that means that after time the effect would fade from bloodlines if it is not renewed (two tieflings getting together). Just like any trait in real life evolution may eventually go away unless it is renewed.
As you state, there's no reason why an outsider can't be native to the material plane without possessing the native subtype: they simply wouldn't have the extraplanar subtype.
Well first, even if the devil is born to the material plane doesn't mean it is native to it. It MAY be, but it is hardly a certainty. It would more likely not possess the extraplanar subtype, but even that is unlikely. But in either case, I still fail to see why you say the EP is the defining factor here.
There's no reason why a planetouched or other outsider (native) can't be native to a plane other than the material plane: they would simply possess both the native and the extraplanar subtype on the material plane.
Equally unlikely as the devil. If an aasimar goes to an aasimar colony on Limbo (for example) and has a bunch of aasimar kids, those kids could have kids, and so on for generations. All of those great grand kids would almost certainly STILL be native outsiders, because they are made of the building blocks of the material plane. They may separately be naturalized to Limbo and lose the extraplanar subtype but that process would take a long time too and is not guaranteed. In fact the only reason I am even hedging on this (as I doubt there are very many documented cases) is because I can think of a few planar anomalies like this, mostly involving gods (vecna specifically) being 'born to' specific planes and then being unable to be banished once there - but those are deviations and not the norm.
As such, the native subtype is confusingly named because it can apply to outsiders that are not native to the material plane and does not always apply to outsiders that are native to the material plane, and the word "native" itself is always used with reference to outsiders to indicate which plane they are native to.
The native subtype is only confusing if you use it in another meaning than what it is intended for. This relates back to earlier in this post when I ask if it would be less confusing for you if the word native was instead 'material' as it means the creature is made of the material plane, even if not born there they are still 'of' there. It is meant to be applied generally as types and subtypes do, not specifics. In general devils are Outsider (evil, lawful, baatezu, EP) but have you ever looked at the Kyton (chained devil)? It lacks the baatezu subtype, it is an exception not the rule though.
The outsider type is confusingly named because you can have outsiders that are native to the material plane, which grammatically-speaking means they aren't outsiders.
Which is why the native subtype exists. Generally outsiders that become
native to the material plane become Outsider (native) for just this reason. As I said, the term (native) means NOT-outsider to the outsider type. Same as a not-dragon subtype for the dragon type. It is a little odd, certainly, but it properly explains planetouched.
But personally outside of having an odd fixation with the EP subtype and maddenly going around in circles I don't entirely disagree in areas. When I did my retype for my own OGL system, I realized that I don't really need a native subtype - I made existing natives into humanoids or outsiders properly. With that said, I don't disagree with the outsider type - and most versions I have seen that have types even resembling what they do in DnD have similar distinctions.