I have an alien race that is carbon-based, like life on Earth, but this alien life uses different essential elements in their biochemistry than those elements used on Earth.

I'm trying to come up with a a naming element convention that the aliens might use that allows them to uniquely distinguishes between our (Earth-based) carbon-based life and their alien carbon-based life.

For example, suppose that the aliens contain hydrogen, carbon, oxygen, but not nitrogen. Hypothetically, these aliens dub life on Earth as nitrogen-unique life forms. (This is one example, but I'm wondering if there is something a little more scientific or concrete.)

What is a naming element convention that distinguishes different forms of life based on the unique essential elements in their biochemistries?

  • $\begingroup$ Sounds perfectly cogent to me. Besides, an alien race would most certainly view humanity as distinctly different, much like we distinguish between ourselves and other animals... $\endgroup$ Mar 17, 2015 at 14:01
  • $\begingroup$ Interestingly enough sugar does not contain nitrogen. $\endgroup$ Mar 17, 2015 at 14:03
  • $\begingroup$ What do you mean by :atomic count"? $\endgroup$
    – HDE 226868
    Mar 17, 2015 at 15:23
  • 1
    $\begingroup$ While nitrogen is important, it's not the base. Consider all the trace elements required for (at least mammalian) life - iron, copper, zinc, potassium, sodium, chlorine - oh, there's a good one: can we be described as chlorine-based? Nitrogen is not a viable base because free nitrogen winds up bound in (among other things) N2, and it takes a whole lot of energy to make it available. $\endgroup$ Mar 17, 2015 at 16:07
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    $\begingroup$ This could just be me, but I still don't understand the question. $\endgroup$
    – HDE 226868
    Mar 17, 2015 at 22:45

5 Answers 5


Calling something an "X-based life form" (where X is a chemical element) is useful exactly if you are trying to distinguish it from some other life form which is not X-based.

If your aliens are thinking of other forms of life which do not use nitrogen, then yes, in principle "nitrogen-based" is a reasonable term to describe us.

Wikipedia has an interesting article on proposed alternate biochemistry schemas which may be of some use.

  • $\begingroup$ This would be especially useful if there are other races that are carbon-based but not nitrogen-essential. In that situation "carbon-based" might be inaccurate. $\endgroup$ Mar 17, 2015 at 19:34

If the question deals with what is essential, rather than what a life-form is based on, then yes, you can certainly call Earth-based life nitrogen-essential. No problem.

But why are your aliens fixated on nitrogen? Let's look at a few other elements that are essential, at least for most species (in order of atomic weight):













And I'm sure there are more, but I'm too lazy to think about it.

So, what's so special about nitrogen?

  • $\begingroup$ Is the word 'essential' not specific enough? I am currently struggling to find a better substitute. $\endgroup$ Mar 17, 2015 at 19:44

They might call earth life as "nitrogen-dependent".

Nitrogenated life. Or something like that.

Lets suppose they use arsenic in most of their lifeforms, we could call them arsenated lifeforms or arsenic-dependent (For us arsenic is quite toxic). This might be reciprocal. But, nitrogen is a too important component of our lives, all proteins contain it.

Its the base of aminoacids. In a aminoacid, a amine group is linked to a carbon compound and this compound is linked to a carboxylic acid group. Without nitrogen theres no aminoacids, without aminoacids you have no proteins and so on.


Nitrogen in humans is essential to amino acids and thus, proteins. Perhaps the aliens' bodies synthesize their own proteins using phosphorus instead.

For example

"Carbos" versus "Phosphoros"


Have the element that is found in highest amounts be what it is called. Though small disconnect with "Carbon-based."

Or maybe "(compound X) based" for highest occurring compound, like h20, you could say we are "Water-based."


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