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Biology for Worldbuilding: Immutably Mutable Genetics of Octopuses

[Above: Drawing of Octopus vulgaris by  Comingio Merculiano (1845-1915) circa 1896, published in Jatta Giuseppe (1860-1903). Public Domain via Wikimedia Commons.] 

This post is the first in the series aimed at people who write speculative fiction–sci-fi, fantasy, horror, etc–and are looking for worldbuilding inspiration. In each post, we’ll take a look at a biological trait and explore how that trait might shape a species and the cultures/societies said species might form. Since these posts are mostly about hypothetical alien or fantasy worlds, I want to stress that these posts are thought experiments and highly spectulative.

Humans cultures are obsessed with the idea of inheriting fixed traits–such as nobility, honesty, and magical abilities–from ancestors.  It’s the basis of feudalism and hereditary rule. It’s at the root of the Nature vs. Nurture debate. And today, it’s one of the main reasons why people get their genomes sequenced.  The concepts of DNA and bloodlines will probably be used to justify racism, power grabs, and high fantasy plot twists for decades to come.

Thanks to DNA sequencing studies, the evidence is pretty clear: many traits and predispositions to certain traits can be passed down from parent to parent. People still tend to assume that traits–especially physical ones and “innate” abilities–are more or less determined by DNA and that the environment’s role, if it has one, is secondary.  After all, you can’t just rewrite your own genetic code, right?

Well…if you’re an octopus, squid, or cuttlefish, you kind of can…at the RNA level, anyway.

That, imho, would be an interesting trait for a sci-fi alien or fantasy beastie to have, and in sentient, society-forming life forms, it could have a profound impact on how they behave and see themselves.

[Flamboyant cuttlefish doesn’t care who Jon Snow’s parents are.] via GIPHY

First, some science explanation:

Octopuses, squid, and cutteflish–collectively known as the “coleoid cephalopods“–transcribe the sequences in their DNA into RNA pretty much the way everyone else does, but then, they add an extra step that allows them to make proteins that aren’t encoded in their genomes: They have enzymes that pull As, Gs, Cs, and Ts off of the RNA backbone and replace them with new base pairs in a process called RNA editing.

Mammals and other animals can edit our RNAs and do have the RNA-editing enzymes floating around in our cells, but we don’t use the ability very often. RNA-editor enzymes are very picky and can only edit base pairs that are flanked by specific sequences. (If you want to get especially specific about it, an RNA-editing target has to be surrounded by base pairs that allow the RNA to tie itself up in a knot with the target sticking out.)  For our purposes, the thing you need to remember is that: octopuses and company can alter the proteins their cells are making very rapidly by rewriting their RNA, and they do it all the time.  

That ability can be useful for quickly adjusting to cold water or in neurons that need to be able to respond to cues quickly in general. But it comes with a catch.

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