Alien DNA kinda useless

[Kai]

I'm lv20, saw that my health was in the 600s anyways, and removed the background using the doctor, and didn't see ANY change in my hp being that drastic...

So yeah it's kinda useless as it reduces your food and medical effectiveness, especially food.

[Schutzengel]

Its not useless. Oxygen is calculated the following way (player.getav oxygen):

Oxygen = (100 x Fitness) + Alien DNA
Alien DNA = 50

While the Fitness Perk doesnt multiply with Alien DNA, your max Oxygen is:
130 without Alien DNA
180 with Alien DNA

Thats almost +40% more Oxygen. The food and healing debuff can be ignored later in the game when you get the automatic healing Perk.

Though I agree with the HP part of the Trait. You get +50 HP with Alien DNA but again it doesnt multiply with the Wellness Perk. Since you get +10 HP each Level-Up the HP benefits eventually become obsolete.

Alien DNA thus is solely a huge Oxygen buff. Its: Alien Lungs.

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Edit: It seems that Oxygen regeneration is based solely on your max Oxygen, taking Alien DNA into account. It takes roughly 35 seconds ro regenerate a depleted O2+CO2 bar while not being encumbered.

Without Alien DNA you regenerate 130/35s = 3,7 Oxygen/s
With Alien DNA you regenerate 180/35s = 5,1 Oxygen/s

It takes the same time to regenerate Oxygen, so whatever you do that depletes Oxygen, you can do it for roughly +40% longer if you have Alien DNA.

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Edit2: Serpents Embrace increases Oxygen by +25. Again, regeneration is based on the updated value. However its only half the benefit of Alien DNA and it forces you to jump regularly or suffer an Oxygen penalty.

Alien DNA is the best Trait that offers a numeric boost but doesnt alter gameplay.

[Kai]

Oxygen isn't a main issue once you get a spacesuit with 75% O2 reduction when moving under encumbrance. Then having modifications and magazine perks that makes that even more efficient. The main use of removing Alien DNA is to use Nutrition with higher levels of food buffs, like say +2~5% EXP instead of +1~2XP, at 50% more duration, etc.