# Type Alias: Backbone

[**lifecycle-kit**](https://jonbogaty.com/lifecycle-kit/api/readme/index.md)

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[lifecycle-kit](https://jonbogaty.com/lifecycle-kit/api/readme/index.md) / [chem](https://jonbogaty.com/lifecycle-kit/api/chem/readme/index.md) / Backbone


# Type Alias: Backbone {#type-alias-backbone}


> **Backbone** = `"C"` \| `"Si"` \| `"S"`

Defined in: [chem/biochemistry.ts:29](https://github.com/jbcom/lifecycle-kit/blob/074e4e7b8038d3e2de9eb44c4b5b5aee0ef02b48/src/chem/biochemistry.ts#L29)

Which chemistry life is built from — derived, not assumed.

This is not speculative xenobiology. Everything below is the ordinary
behaviour of the periodic table: bond energies we have measured, hydrolysis
we have observed, abundances we have counted in stellar spectra. Given a
world's temperature and composition, the chemistry that follows is not a
choice anyone makes. It is what happens.

On Earth, carbon wins decisively and the reasons are quantitative: carbon
self-bonds at 346 kJ/mol against silicon's 226, and carbon is roughly seven
times more abundant. Long chains need both, so carbon it is.

But two of those facts are conditional. Si-Si and Si-O-Si chains hydrolyse
in liquid water — which is why silicon chemistry is discounted for Earth and
seriously discussed for hot, dry worlds, where silicones are stable and
carbon chains are the ones falling apart. And abundance is set by a galaxy's
enrichment history, not by anything universal.

So the backbone is SCORED from this world's actual temperature and actual
abundances, and whatever wins is what tissue is made of. A player who lands
on a hot silicate world is not playing a science-fiction variant. They are
watching the same rules produce a different outcome.