a small tooth

Since there's some people who've expressed interest but haven't ever seen or read Dune, let me give a quick summary of the relevant plotline: Dune follows Paul Atreides, as he continues the ongoing blood feud with the Harkonnen family and also finds out he's a result of a program by the Bene Gesserit sisterhood to create a manufactured messiah, using the same tactics as contestants in the Westminster Dog Show: breeding together the weirdest people you've ever seen, until they check off all the boxes for the space-witch kennel club.

The Bene Gesserit, via years of intensive training and drinking a specific kind of poison, are able to unlock a portion of their genetic memories, granting them the wisdom of the ages. Paul's mother undergoes this process, and Paul eventually does too, unlocking his entire bloodline. This gives him so much knowledge that he's able to predict the future by seeing how the past played out. It goes great for everybody. Don't worry about the holy war, I'm sure that'll be fine.

Right, so, first off, let's just make this a clear no: The genome does not contain memories. There are two things we have that could be termed genetic memories, and neither of them are what Frank Herbert describes.

First, we have instincts. These are hard to positively identify in humans because we're such social animals and love learning things by imitating each other, but we do have some that we can point to: babies crying, the instinct to nurse, how to swallow food without choking, that kind of thing. These are things that just help you not die.

And not dying is good! That's just not what we're looking for here.

What the genome itself does have are little chemical doodads that can be broadly classed as epigenetic modifications: "epigenetic" literally meaning "above the genetic", so this is an added layer of coding, separate from the DNA itself, that alters how genes are used, rather than changing the genes themselves. Unlike the genome, epigenetic modifications are dynamic, and they aren't all the same across the body. They're different in every cell, they can change throughout the day, and respond to different conditions. Some last fractions of a second, some can last for basically a whole lifetime. A subset of them can even be inherited from your parents!

This means that events within the life of a single individual can in fact alter the way an offspring's genes are used, moving faster than the pace of genetic mutation. That's often very slow, changing the makeup of an entire population on the scale of multiple generations. But if you have a famine? You need something quicker.

And indeed, that's one of the first places we saw evidence for this kind of epigenetic inheritance. The Hongerwinter of 1944-1945 that starved the Netherlands during WWII has resulted in greater rates of several chronic health conditions in granddaughters of mothers who were pregnant during the famine. This is called transgenerational stress inheritance, where extreme physical or psychological hardship can have long-lasting effects in a family, even if parent and child never meet.

These studies controlled for all the factors that might complicate these findings, leaving only the intergenerational effects of starvation as a clear culprit. So, if we know that parents can pass down their stress responses to famine, or other epigenetic factors, what else might be carried? Could you inherit memories?

Well, no. While we don't have a great understanding of how experiential memories are formed (as opposed to instincts and reflexes), remember back to something. I said earlier: epigenetic marks are not shared across the body. Even if epigenetics probably plays a component in memory formation, your brain and ovaries are in a long-distance relationship, with shitty cell service. This is why we can have vague, intergenerational stress responses encoded in epigenetics, but nothing more concrete than that.

Also, the majority of epigenetic marks get stripped off during early embryonic development, leaving only a few that get carried over. There's a lot we're still learning about it and it's an active area of research, but hopefully you can see why you're not humming your great-great-great-great grandmother's favorite songs unless she left the family some sheet music.

But what if we want to bullshit a reason for how genetic memory could work, in a universe that isn't ours, with genetics and epigenetics that work completely different from our own?

jpegs.

I have to emphasize, what I'm about to propose is not the way anything works in real life. This is pure science fantasy.

Compressing data is a very useful process that we use all the time in computing and in communication. Like, a workout routine will tell you "do two thousand steps today" not "step. step. step. step. step. step. step. step. step. step." for three pages. And if you were wondering, yes. I actually checked how many pages it would be. Compression acts like that: a series of instructions that tell you how to build a digital file, do a task, or make something. Some methods are lossless, which means that the compressed instructions will always result in the same end product. Others are lossy, which means that certain data we find less important is thrown out entirely, preserving a decent facsimile of the original template. PNGs are lossless, and often bigger. JPGs are lossy, but are smaller file sizes.

And we need a lot of storage space to pack in twenty bajillion generations into one brain.

A hypothetical system of genetic memory would require compressing vast amounts of information about how to structure a brain, on a level of detail that our actual genetics doesn't do. We all end up with brains shaped approximately the same way, but not exactly the same. Everybody has an amygdala, and it grows into a predictable structure, but this ain't exactly precise. Brain cells show up, they go where they're needed, and nobody's taking role call.

I mean, not unless you're somewhere like the Allan Brain Institute, but even they don't pretend like they're gonna do a one-and-done here. There is also the deceptively named paper "Neuronal wiring diagram of an adult brain", which is an amazing achievement that takes a couple sentences before you find out they're talking about an adult fruit fly.

Anyway! Connections between neurons start out quite wild and woolly, then get pruned back as we learn: this process basically makes highly complex biological circuits that encode skills, memories, habits, addictions, and everything else you can think of. Like, literally. Everything you can think of is determined by these connections. And some you don't think about, like unconscious movements, subconscious processes that run in the background, etc. etc. As mentioned, some instincts are pretty hard-wired in there, indicating that those structures are constructed to a high degree of similarity in everybody.

What we would basically need would be to extend that a lot. We'd need to add in systems that encode bloodline-specific patterns of neural circuit formation, which are generally not consciously accessible, but can be consciously activated if a person is exposed to the right psychoactive compounds, temporarily or permanently unlocking some other neural mechanism that makes the switch.

If we wanted to make this only mostly entirely impossible, we could say that this is an epigenetic mechanism, one that isn't wiped out during the purge of epigenetic marks within the first few days of development. I want to emphasize, this would require a lot more of these marks to be maintained, but hey, some preservation is possible, so we can say more could stick around. Once the brain develops, it starts a process of preferentially pruning connections between neurons, to make the circuits that encode these ancestral memories. The epigenetic encoding of ancestral memory would be basically compressed into a series of complex but lossy biochemical algorithms, which would allow memories to be retained up to a point. Each generation would lose some data, freeing up more for the next generations. The brain can hold a lot, but even when bullshitting, I'm not willing to say we've got anything like infinite capacity in there.

We still have the logistical problem of getting this encoded information from the brain of a parent to their freakin' gonads, but I'll take a swing at that as well.

Make an entirely new regulatory system in the body. When a memory is formed, nerve impulses that reflect the new structure of the memory are sent to a purely hypothetical organ that can transmit the information. I have two options I can think of:

The organ creates cells, which act as messengers. These cells produce RNA that signal where in the genome needs new epigenetic marks. These circulate through the bloodstream, eventually finding the gonads, where they interact with tissue there. The signal is then propagated through to developing eggs or sperm via… something. Gap junctions, I guess, I don't study intercellular signalling.

The organ creates RNA that is packaged into endogenous retrovirus-like particles and sent into the bloodstream. What the hell does that mean? Well, your DNA has ancient virus genomes accidentally stuck in it, some of which have been coopted for regulating cell behavior. But sometimes, at specific stages or development or in specific biological fuckups, some viral genes get properly reactivated and actually make virus-like particles! Usually it is not ideal when these regain the ability to be infectious, but we can make that a thing for Dune! Give them surface proteins that latch onto reproductive cells and infect them with RNA, acting as both a messenger for the modifications we need, and to make more viral particles. Preferably without exploding the cell in the process, because that would be bad.

I cannot stress enough how much bullshit I'm having to put out here while ignoring the many gopher holes of various biological impossibilities, trying not to fall into one lest I break a leg.

If we want to make this even more impossible, we could say the DNA itself is being altered. That would get around the issue of epigenetic marks getting removed during reproduction and also give a plausible reason why these memories wouldn't be accessible without a chemical signal that activates the brain to form new connections, plus also creating a handy way to cause the dreaded status of Abomination. What's that, movie-watchers and others ask? Good question! Let's ask Horror Movie Face Lady Jessica what that's all about.

Abomination is what happens when genetic memories are unlocked in someone who is not sufficiently trained to control the weight of countless generations bearing down on their consciousness. Strong personalities within the memories can go progress from speaking to the original personality, influencing their behavior, or even go as far as to suppress the original personality entirely, producing an effect that basically manifests as possession by a ghost in their genes.

While Dune itself doesn't include any Abominations per the story as written, the line may be fuzzy, and Dennis Villeneuve seems to have leaned into that. Jessica's personality radically shifts after she unlocks her genetic memory. We've arguably witnessed manipulative behavior from Paul's visions as well, which pushed him into doing things he hadn't wanted to do, and ending with a personality shift similar to what happened to Jessica. Some of the things he says in the movie are not found in the books: his realization that both he and his mother are Harkonnens by lineage has more weight in the movies, with his comment being "We're Harkonnens. So this is how we'll survive: by being Harkonnens."

So, Villeneuve may have been making the suggestion that Paul, trained in the Bene Gesserit ways but not sufficiently trained to safely unlock his genetic memory, may have been partially taken over. It's the best explanation I have for why the Reverend Mother Mohiam calls him "Abomination" in Dune: Part Two, rather than the I-won't-totally-spoil-who she directed that toward in the book. Jessica probably had something similar happen, as she wasn't actually on a path to be a Reverend Mother.

Oh hey and you know who really didn't have training?

I'm sure that won't be a problem later.

We already have regulatory regions coded into the genome, so adding in more isn't a stretch. They would probably be subject to more rapid degradation than genes themselves though, because they're not critical to, y'know, living. So expect mutations to up in these regions, leading to imperfect recall, or even false genetic memories.

But how would you actually make changes to the genome within the lifetime of a person? In humans, outside of a couple of really special contexts that aren't relevant here, that's something that doesn't happen.

Well, it's simple! We just need humans to be like bacteria.

no, that's not it.

CRISPR/Cas gene editing is a technique we scientists have stolen from distant cousins of strep throat, and we're using it for genome editing. Basically, bacteria can get infected by a virus too, and they don't like to be infected by a virus. So, because they're a single cell, they need in-house solutions to find viral DNA in their own genomes and snip them out. Geneticists have used that for gene editing in laboratory settings: add in a DNA template sequence for the cell to use as instructions for what to put in the gap, and bam, you can insert a new DNA sequence. There are a load of caveats, but that's the basic idea. Load a CRISPR/Cas system into one of the fictional delivery mechanisms I mentioned above, and you've got a genetic memory.

I have to stress that humans are not, in fact, bacteria, having a programmable CRISPR/Cas system in your body would probably be a great way to shred your genome due to some side effects it can cause when it gets a bit too exuberant, and I am not proposing this as any sort of real thing. How would you encode the guide and repair templates? Not my problem! I've already thought about this way more than Frank Herbert did.

Now, this could in fact lead to terrible psychological effects, beyond the Abomination thing. Like, beyond destabilizing your genome, obviously. Like, there's a lot of sensory information that we filter out 99% of the time. What's your tongue feel like right now? You probably weren't conscious of that until I mentioned it, and now you're thinking about it. Imagine that, but it's twenty-five thousand years of your ancestors. People who have exceptionally strong autobiographical memory often report all sorts of distressing events sticking with them, because they don't get as much relief from forgetting details over time, and, unlike in Dune, it can make it harder to plan for the future, because there's an often exhausting parade of memories running "in splitscreen" all the time.

The fact that we only see one character in the books go absolutely bat-guano because of ancestral memory seems like it's lowballing the danger here.

In summary!

Dune has a major plot point about genetic memory, which is unlockable with special training, partially accessible with special genetics, and by overdosing on worm juice.

This is not a thing in real life, with intergenerational memory limited to very basic instinctual behavior, and less literal memory that tweaks the likelihood of certain health outcomes depending on extreme stress exposure in recent previous generations.

If we wanted to bullshit our way to making genetic memory a thing, we would need to compress a lot of information, and transfer that information from the brain to the gonads via a Rube Goldberg machine of biology.

This machinery would probably involve memories being encoded via epigenetic information (more malleable, but more likely to get erased, harder to do the plot points around unlocking them via special training), or genetic information (more permanent, matches the story more closely, but more likely to go absolutely bananas and break you)

The transfer itself would either be done by some sort of fictional class of transport cells, or a fictional class of endogenous retroviruses, the little viral pals that hang out in your genome.

Adding the modifications that encode memory would either be done by altering some pre-existing class of epigenetic targeting system, or by giving us a CRISPR-Cas9 system, something only found in bacteria IRL.

I'm not done yet, though. Because this only talked about the concept of genetic memory, not some of the major plot points around accessing it, and who can access it.