From XNA to Xeno Nucleic Acid
By Nelson McKeeby
The X Meant I Didn’t Know
When I first introduced the term XNA in Negentropy, it didn’t refer to xeno nucleic acid. It didn’t have a precise meaning. My intention was to create genuinely alien organisms for the BEMs, and I needed a way to convey that their biology was based on something other than the familiar machinery of terrestrial life. I understood DNA and RNA well enough to recognize their role in carrying biological information. However, I lacked the chemistry to provide an alien equivalent. XNA became the label I used to fill in that gap.
This was part of a broader pattern in my early writing. Whenever I used an X in a technical term, it often indicated that I was venturing beyond my expertise. X-Tech followed a similar principle. I could envision a technological direction I wanted to explore and sometimes estimate what an advanced version might achieve, but I didn’t necessarily possess the engineering knowledge to make it feasible. The X wasn’t a scientific designation; it served as a self-imposed warning that the explanation was incomplete.
In 1979 and 1980, this didn’t bother me as long as I was clear about the limitations of my incomplete idea within the game. I was willing to leave certain mechanisms unresolved if the consequences could still be beneficial. The Negentropic Cylinder itself relied on a fictional relationship between entropy and experienced time. Dwimmer later allowed for extraordinary mechanisms while ensuring physically coherent results. XNA belonged to the same family of inventions, but it was less developed than either. My goal was to achieve a specific outcome: some BEMs should be biologically so foreign that assumptions based on ordinary terrestrial life would be invalidated. However, I lacked a molecular explanation for why this would happen.
Creating the BEMs Alien
To make the BEMs truly alien, I needed to delve deeper into their biology and explore the molecular mechanisms that could explain their extraordinary characteristics. I wanted to create a world where the laws of biology were not as predictable as they are on Earth, and where the BEMs could challenge our understanding of life itself.
The primary objective of XNA was to prevent BEMs from becoming ordinary monsters with peculiar appearances. I didn’t want every strange organism in the future to be a mutated bear, oversized insect, irradiated reptile, or another terrestrial animal altered by catastrophe. Some creatures were intended to originate from other worlds, and I wanted that alien origin to have consequences beyond mere shape.
A truly alien organism should create biological uncertainty. Its tissues might not react to the same toxins, its pathogens might not behave like terrestrial pathogens, and its food requirements might not align with familiar nutritional categories. A wound inflicted by one might present chemical challenges that a physician had never encountered. A body found after an encounter could be valuable because examination might reveal the type of world the organism came from or the biochemistry that sustained it.
In those early years, I could describe the gameplay consequence much better than the molecular cause. By stating that a BEM used XNA, I could mark it as biologically alien without pretending I had already determined an alternative genetics. The term created a boundary around my ignorance, allowing me to ask questions. However, I couldn’t yet provide satisfactory answers to all of them.
It’s important to note that I don’t consider the early XNA idea a scientific prediction. I didn’t invent an alternative nucleic-acid chemistry in 1979 and then wait for laboratories to confirm me. Instead, I created a name for a fictional problem. The intriguing aspect emerged later when scientists developed a real concept whose terminology and purpose overlapped with the space I had left open.
XNA in Campaign 80
XNA proved to be incredibly useful almost immediately after Negentropy was actually being played. During Campaign 80, the group decided to accompany a ranger on a hunt for a BEM. I wanted the players to have more than just reasons to fight monsters, and this encounter presented an opportunity to treat the organism as something that could be studied. If the creature was biologically alien, then observing it, collecting samples, examining its behavior, and learning how it reacted to its environment could all have practical value.
This encounter marked one of the earliest instances where knowledge became a form of advancement. A deceased BEM could provide tissue samples, anatomical clues, evidence of sensory systems, or information about the types of damage that affected it. A living encounter could reveal behavior, feeding patterns, movement, or environmental preferences. The players could carry these observations into subsequent encounters, using scientific knowledge gained from one organism to protect themselves against others.
I didn’t require every BEM to share an identical biology for this concept to work. What mattered was that investigation accumulated valuable information. If one creature reacted adversely to a specific chemical environment, the players could test the same possibility with another before assuming it was effective. Similarly, if a particular tissue proved resistant to an ordinary drug, that taught the team not to take compatibility for granted. The game rewarded caution, sampling, comparison, and memory.
XNA played a crucial role in making this possible by informing the players that familiar biological rules might not be universal. It didn’t provide them with the new rules; they had to discover them themselves.
A Placeholder That Lasted
The surprising aspect is how long the placeholder endured. Negentropy continued to expand through new campaigns, manuals, creatures, and attempts to elucidate its biology. My scientific knowledge also improved, but there wasn’t a single moment in the early years when I suddenly acquired a comprehensive theory of alien heredity. XNA remained relevant because it consistently identified the problem correctly, even though the explanation behind it was inadequate.
One of the challenges of a long-running science fiction project is that a term can become ingrained in stories and rules before the writer fully comprehends its intended meaning. There’s always a temptation to either defend the old explanation because it’s established or to eliminate it entirely once more accurate information emerges. I’ve generally preferred a third approach: preserve the historical reason behind the term’s existence and enhance the current explanation when research provides a better understanding.
The X in XNA was particularly well-suited to this process because it originated as an admission of uncertainty. I wasn’t compelled to defend a detailed fictional chemistry that contradicted later scientific discoveries. There wasn’t much chemistry to defend in the first place. The term essentially stated that the creature utilized an unknown hereditary system. This left room for the system to become more specific in the future.
Years later, I came across work by Piet Herdewijn and Philippe Marlière that provided XNA with a scientific meaning I hadn’t previously attributed to it. In 2009, they published “Toward Safe Genetically Modified Organisms through the Chemical Diversification of Nucleic Acids” in Chemistry & Biodiversity. They used XNA to refer to “xeno-nucleic acids,” synthetic genetic polymers whose chemical backbone could differ from the ribose and deoxyribose systems of RNA and DNA while still carrying genetic information.
Their issue wasn’t mine. They weren’t trying to explain alien monsters in a role-playing game. They were exploring synthetic biology and the possibility of genetic systems chemically separated from ordinary DNA and RNA. To me, the paper demonstrated something far more significant than the coincidence of initials: the chemical architecture used by terrestrial life wasn’t the only conceivable way to construct an information-bearing genetic polymer.
This provided me with the scientific foundation that the original game term lacked. I had used X because I didn’t know what the molecule was. Herdewijn and Marlière used X for xeno and described a genuine family of chemically modified nucleic acid systems. Their X made more sense than mine.
I formally adopted that meaning into Negentropy in 2015. From that point on, XNA ceased to be merely my old shorthand for unknown alien genetics and became Xeno Nucleic Acid within the setting. This change didn’t require abandoning the original purpose. It finally gave that purpose a coherent biochemical direction.
What the Scientific XNA Actually Changed
Adopting the scientific concept transformed the questions I could ask. Ordinary DNA and RNA utilize familiar combinations of nucleobases, sugars, and phosphate-based backbones. Xeno nucleic acids opened the possibility that a genetic system could retain some of the information-handling functions of nucleic acids while altering crucial aspects of that chemical architecture.
That doesn’t prove that extraterrestrial organisms use XNA, and I’ve never needed it. The scientific work provided Negentropy with a plausible framework to explore the consequences of such a scenario. Once the hereditary polymer itself differs, compatibility with the rest of terrestrial biochemistry cannot be assumed. Enzymes are specifically shaped to recognize particular molecules. Polymerases, nucleases, repair systems, receptors, transport systems, and metabolic pathways all operate through chemical fit. Alter the underlying chemistry, and many ordinary biological interactions may fail, weaken, or require entirely different machinery
The modern Nomiconus develops XNA in this direction. Xeno Nucleic Acid is considered an alternative genetic framework where the familiar sugar or backbone architecture can be chemically modified while retaining the ability to carry information. The book then takes the crucial step for gameplay: organisms built on such frameworks can be enzymatically incompatible with DNA-based terrestrial life.
This incompatibility finally provided a tangible mechanism for something Campaign 80 had only suggested. The BEM could be alien all the way down to its molecular machinery, and this difference could have profound effects on medicine, disease, digestion, toxicity, reproduction, and laboratory analysis.
Alien Does Not Mean Invulnerable
A useful alien biology cannot simply be an excuse to dismiss the applicability of ordinary science. If XNA made every BEM immune to every terrestrial chemical, impossible to infect, impossible to poison, and unreadable by any laboratory method, it would become another form of magic. The scientific concept is more intriguing because incompatibility generates both protection and vulnerability.
A biological system relies on interactions among numerous molecules. If these interactions are highly specific, a foreign chemistry may not participate in them. For instance, a terrestrial enzyme may not recognize an XNA substrate, but an XNA organism may also lack the enzymes required to utilize a terrestrial nutrient. A pathogen adapted to human cells may be unable to replicate in a creature with radically different molecular machinery, while a pathogen adapted to that creature may find human cells equally useless. A toxin that attacks a specific terrestrial receptor may have no target, while a simple environmental compound that terrestrial life tolerates could interfere severely with an alien pathway.
That’s precisely the kind of asymmetry I desire in Negentropy. “Alien” becomes a reason to investigate, not a universal defense statistic. The characters cannot assume that ordinary antibiotics will work, but they also cannot assume that the organism is beyond intervention. They need samples, observation, comparative testing, and an understanding of the actual mechanism present.
This brings XNA back to its original gameplay purpose: knowledge improves survival.
The Difference Between a Name and a Mechanism
The history of XNA taught me something valuable about science fiction terminology. A name can preserve an idea for a long time without providing an explanation. That can be beneficial if I remember that the name is not the mechanism.
In 1979, XNA introduced me to the concept of a BEM’s hereditary system as alien. However, it did not provide details about the atoms involved, the replication process, the enzymes required, or the protein encoding mechanism. If I had treated the acronym itself as an explanation, there would have been nothing to research later. By recognizing the scientific structure that was missing, I was free to fill in the gaps when a better idea emerged.
This is also why I’m cautious about backdating modern explanations. The current XNA material in Negentropy is significantly more sophisticated than the Campaign 80 version. It would be historically inaccurate to claim that I comprehended alternative polymer backbones when we first encountered a BEM with a ranger. I didn’t. The early game had the design principle and the question, but the later game acquired the chemistry.
For a project that has existed for decades, maintaining these two histories separate is crucial. The old page reflects my beliefs or imaginations at the time, while the modern sourcebook presents the current setting. Both are valuable, but for different reasons.
X as a Marker of Depth
Reflecting on my early use of X, I believe it reveals something broader about my design approach for Negentropy. When I reached a point where I knew the story required an answer but lacked the knowledge to construct one effectively, I often marked the gap instead of filling it with elaborate nonsense. X-Tech represented advanced technology without a complete engineering explanation, while XNA conveyed alien biological information without a molecular explanation.
This approach didn’t always yield accurate science. Sometimes, the placeholder persisted longer than necessary. However, it created a space for research to enter later. The key discipline was recognizing that the X didn’t grant me permission to cease thinking.
The research method was most effective when the placeholder gradually narrowed. An X-Tech device should acquire comprehensible limitations even if its internal mechanism remains advanced. Similarly, XNA should provide concrete information about biochemical compatibility rather than merely implying “weird biology.” Dwimmer should necessitate a coherent physical outcome even when its mechanism remains extraordinary. In each instance, the unknown aspect becomes smaller as the consequences become more clearly defined.
Negentropy’s evolution without losing its core structure is attributed to this process. I can retain the essence of an old concept while replacing its inadequate explanation.
Research Caught Up, but Not in the Expected Way
A tempting narrative suggests that an eleven-year-old invented XNA in 1979, and science validated his theory thirty years later. However, I believe this is not the case. My intention was to represent alien genetic material, and I used the letter “X” in front of “NA” because it symbolized something I couldn’t yet comprehend. Herdewijn and Marlière later proposed xeno-nucleic acids based on real chemistry and synthetic biology. The similarity between our work and theirs is intriguing precisely because the paths we took were so divergent.
What their research provided me with was not validation, but rather a more effective tool.
This distinction is crucial in my approach to research. The objective is not to scour the literature until I find something that resembles an old Negentropy concept and then claim prediction. Instead, the purpose is to enhance the idea. If a genuine scientific concept offers better constraints, I incorporate those constraints. If it demonstrates that an old idea is ineffective, I modify or discard it. If it provides a mechanism where I previously had only a name, that mechanism becomes an integral part of the current framework.
XNA stands out as an exceptionally satisfying case because the original term did not need to be abandoned. The letters persisted while their meaning evolved.
From Speculation to Nomiconus
Therefore, the modern XNA material is the result of two distinct periods of Negentropy interwoven. Campaign 80 provided the purpose. Bioengineered Microorganisms (BEMs) could genuinely be alien, and understanding their biology could aid the players in surviving future encounters. Modern xenobiology offered a framework for rendering that alienness chemically meaningful.
Nomiconus can now explain Xeno Nucleic Acid (XNA) as a genetic system rather than just a label. It can discuss altered molecular architecture and the consequences of incompatibility with ordinary terrestrial enzymes. Healer can inquire whether a human medicine has any reason to work on an XNA organism. Naturalist can treat an unfamiliar organism as a biochemical system that must be observed before making assumptions about terrestrial ecology. An investigator can regard biological residue as evidence whose chemical behavior may reveal that the organism did not belong to ordinary DNA/RNA life.
These are much more robust game questions than the ones I could formulate in 1980, but they serve the same purpose. The creature is not interesting merely because it is difficult to kill. It is interesting because understanding it changes what the characters can do.
That is the continuity I care about most.
What XNA Means to Me Now
Today, when I use XNA in Negentropy, the X stands for xeno. It refers to genetic chemistry outside the standard DNA and RNA architecture, providing the setting with a scientific basis for organisms whose molecular biology can be incompatible with ordinary terrestrial life.
Historically, however, I still perceive the older meaning beneath it. The X once signified my ignorance.
I believe that is an appropriate history for Negentropy. The project has always relied on moving from imagination toward explanation. Sometimes I started with a well-developed mechanism, sometimes with a rough analogy, and sometimes with nothing more than a term that marked a gap in my understanding. The crucial aspect was leaving the gap visible enough for me to revisit it.
XNA began as a fanciful concept for alien monsters. Campaign play transformed it into a reason to investigate biology. Decades later, real research provided a chemical concept that could support the fictional one. In 2015, I adopted xeno nucleic acid as the official meaning, and the modern books have continued to explore its consequences.
The term remained unchanged, but my understanding of it did not.
Scientific Reference:
The scientific use of XNA discussed here is based on Piet Herdewijn and Philippe Marlière’s paper titled “Toward Safe Genetically Modified Organisms through the Chemical Diversification of Nucleic Acids.” It was published in Chemistry & Biodiversity 6, no. 6 (2009), pages 791–808. The paper uses XNA to refer to “xeno-nucleic acids” and proposes synthetic genetic polymers with chemical backbone motifs that differ from those of ordinary DNA and RNA.