The spell description is a bit convoluted as it explains that stat bonuses of the same kind dont stack.
The wording doesnt specifically say it requires natural armor already but it keeps saying "existing natural armor". That seems to be like a bad way to to it stacks with DIFFERENT natural armor bonuses.
What might be confusing you is that Barkskin doesn't provide a natural armor bonus. Rather, it provides an enhancement bonus to whatever natural armor you already have, similar to enchanted armor having an enhancement bonus to its armor bonus.
Humans and other similar creatures have a natural armor bonus of +0, for the purposes of Barkskin, Amulet of Natural Armor, and similar effects that provide enhancement bonuses to natural armor.
This is similar to how you may enchant clothing as if it were armor with an armor bonus of +0.
What might be confusing you is that Barkskin doesn't provide a natural armor bonus. Rather, it provides an enhancement bonus to whatever natural armor you already have, similar to enchanted armor having an enhancement bonus to its armor bonus.
Humans and other similar creatures have a natural armor bonus of +0, for the purposes of Barkskin, Amulet of Natural Armor, and similar effects that provide enhancement bonuses to natural armor.
In other words, you get the enchancement bonus to your natural armour even if you have none innately. So, for a human, you would end up with +2 natural armour after using Barkskin.
This is similar to how you may enchant clothing as if it were armor with an armor bonus of +0.
So wait, can I have +5 parachute pants?
This is similar to how you may enchant clothing as if it were armor with an armor bonus of +0.So wait, can I have +5 parachute pants?
Yup. With a Magic Vestment spell, you can have +5 parachute pants.
You don't even need to refer to magic vestments, the answer as correctly pointed out by Saethori is found within the spell description.
A creature without natural armor has an effective natural armor bonus of +0.
What might be confusing you is that Barkskin doesn't provide a natural armor bonus. Rather, it provides an enhancement bonus to whatever natural armor you already have, similar to enchanted armor having an enhancement bonus to its armor bonus.
Humans and other similar creatures have a natural armor bonus of +0, for the purposes of Barkskin, Amulet of Natural Armor, and similar effects that provide enhancement bonuses to natural armor.
In other words, you get the enchancement bonus to your natural armour even if you have none innately. So, for a human, you would end up with +2 natural armour after using Barkskin.
This is similar to how you may enchant clothing as if it were armor with an armor bonus of +0.So wait, can I have +5 parachute pants?
No, you cannot.
There is no pants slot in Pathfinder.
This is similar to how you may enchant clothing as if it were armor with an armor bonus of +0.So wait, can I have +5 parachute pants?No, you cannot.
There is no pants slot in Pathfinder.
You have a body slot. Surely it'd take that.
Even then, you could argue it takes the armour slot since it is being utilized as one.