How realistic is a genetic memory?

Question

Many pieces of popculture (like assassins creed or the aboleths in dungeons and dragons) use the concept of a genetic memory. How realistic is this concept?
In particular, I am interested in cephalopods or similar animals. When discussion cephalopod civilizations, many people criticize the idea, because the parents do not form close bonds to their offspring and die before they could teach them anything.
Cephalopods rely on having many babies (r-selection), because they lack any real ways to defend themselves.

Cephalopods are also known for their unique way of evolution through changing their mRNA.
Could a species exist, that passes off knowledge to the next generation directly, by inheriting not a "blank" brain, but basically a copy of the brain of the mother. The individual brain structure would be coded in the DNA of the animal.
Of course, learning and memory would eventually be a problem, but the animal could forget knowledge either after a few generations, or just forget unused knowledge, just like humans do.

A species like that could learn from previous generations without giving up r-selection, or the unique reproduction of cephalopods (that is, dying after giving birth).
How realistic is this concept? Could it evolve naturally? If not, could we eventually create a being that has this ability artificially (through genetic modification)?

Edit:
Most structures in the brain are already fixed before birth (I assume through the genome). For example, the structures that let us see or control basic movements or instincts. So structures can be coded genetically. The question really is, whether structures can be coded while the organism is still alive, so that it can give that modified genome to its offspring.

Answer 1

The concept is sound and has already evolved, for example in the Planaria flatworm and other organisms.

These organisms appear to store memories not (just?) in their brains but in specialized DNA sequences, that are then "re-read" upon occasion. As a result, a decapitated planaria will grow back its head and remember things that happened before it lost its brain.

Injecting cellular DNA (not nuclear DNA) into a Planaria also works. The memories are not active, they appear to need to be "restimulated", but if you teach something to a Planaria after, say, 200 repetitions, the receiving "blank" Planarias will learn it after just one repetition.

There is a SF/Horror story ("David's Worm" by Brian Lumley) in which a boy takes home a mutated Planaria and frees it in a pond, whereupon the planaria proceeds to eat all fishes in the pond, growing in size and acquiring the fish' knowledge

until the child disappears, and the mother breaks out in hysterics when the following morning she sees a shapeless lump of protoplasm sitting in the child's breakfast chair and calling her Mommy.

How it could work

Each brain neuron assigns itself a non-unique semi-random DNA UID during early development; this UID depends on the nearby neurons, in other words the neuron has something akin to a postal code. All neurons in a given neighbourhood will very likely share the same UID or similar versions of the same.

Then, the neuron behaviour is based on the state of its microtubule network - I'm cribbing this off Penrose and Hameroff's OOR theory of consciousness - but this state is initialised and refreshed off specific strings of DNA. This "memory DNA" circulates reasonably freely in the organism as tightly wound DNA minutes, and is "read" based on an initiator sequence that, you guessed it, includes a UID. So, the neurons in the speech center will only ever decode speech-center memory tapes.

We need two more details here - a mechanism for the DNA records to cross the blood-brain barrier, and a mechanism to improve efficiency by "steering" these DNA droplets based on their UID.

Finally, the neurons continuously dump their state in the form of new DNA circles (this is the farthest-fetched part). The "old" circles degrade with time, and are replaced by more experienced ones. Renewed experiences create more circles, and therefore linger in the memory longer.

To do this we can reuse the same strategy employed by telomeres: a DNA record is "born" with a TTL sequence of, say, sixteen blocks containing its UID and a "written" flag. When a record has a "written" flag on the outside, all brain cells kick it out as fast as they can. The record gets dumped outside the blood-brain barrier, where an enzyme that does not cross the barrier removes the "written" flag with low efficiency (it takes on average a couple of hours). When the stripped record comes back into contact with the barrier, it's now exposing a naked UID, so it gets dumped inside the brain and steered where it needs to go. There it gets "read", and the UID is stripped, exposing the "written" flag below. After (say) sixteen cycles, the record has no flags or UIDs and is destroyed.

And when the mother bears a child, the egg's cytoplasm will include a significant quantity of DNA circles (I was wrong, this is the farthest-fetched part). While the child develops, its neurons will usually "boot" incorporating some of these memories. Pregnancy hormones might also influence the process.

( Yeah, the genetic memory is matrilinear :-) )

( This also means that blood transfusions will cause privacy issues unless the blood is treated repeatedly with UID-stripper and flag-stripper enzymes )

Answer 2

Unrealistic, but not impossible

A blind child knows how to smile. A horse knows to start walking just after being born. Most creatures know how to eat and procreate. All this can be considered a form of genetic memory.

For humans, memory in the brain happens in two ways. The neurons in the brain make certain connections. The more a connection is used, the more firm it's established. That is why repeating things over and over, day after day, makes you remember them better and better. The second is a pattern sequence. Some things light up the same area's of the brain, but you remember other things. This is because the way lights up matters. Although completely different, you can compare it with Morse code. It lights up the same wire, but the sequence of beeps make each different. In the end you'll have different combination of structures and different patterns in your brain lighting up for each memory.

The difference between them is the permanency. You know how to eat, because the brain structures for eating are pretty much fixed. This encodes easily into the DNA of your seed and can be passed on. The memory part however is made exactly for memory. It is dynamic. You have an experience, you store it for later reference to improve your survival. But the DNA saves the function, not what's stored in it. Someone with a traumatic experience will not give this to their children.

In short, it's not really possible.

However, I'm willing to see what could make it work

To see how it would work, I would suggest that the DNA for the memory brain structures gets updated if the cephalopod gets more memories. to facilitate this, a whole allele pair is just for memory would be created. Then even complex memories might be stored in the DNA to be grown in the children. How brain memories would trigger certain DNA structures to be added I wouldn't know.

Answer 3

The other (excellent) answers bring up fascinating examples from real biology of creatures that seem able to store memories (to some extent) chemically, which could be directly inherited by offspring. This is a "proper genetic" memory: the actual memory information itself is encoded in genes or other inherited chemicals.

However we can at least speculate about other types of inherited memory, that work at least partly non-generically. Specifically I like the idea of something Half-generic. (Data is not genetic, but ability to read it is).

Some examples to highlight the idea:

• A shelled Cephalopod like creature that stores some/all/backups of its memories in the form of scratch-patterns (braille) on the inside of its shell. If the language of this writing was instinctive and inherited then any offspring to occupy a discarded shell would inherit the memories in that shell: perhaps like a book.

• Nerve link. I have no idea if this is remotely possible, but a nerve connection along the umbilical chord that "downloaded" data into an embryo like a ethernet cable would be an inherited memory, but not a genetic one.

Answer 4

The human genome contains about 3.2 billion base pairs. Due to the way the 4 nucleotides pair up, each pair can hold 2 bits of data. So this translates to just 800 mb. So if you used the entire genome for memory and ignored all the stuff the genome is already doing, you could store about 1 CD's worth of data in the genome. This article estimates that the human brain could have a memory capacity of 2.5 petabytes. To store that much data in DNA would require 1 x 10¹⁶ base pairs of DNA, which is over 6 million times the DNA a human has.

Answer 5

Alternate solution: Memory downloads

I would suggest a possible alternate concept, which achieves the same end but doesn't require fancy DNA methods. Treat memory as data storage, and directly download memories from mom to baby. If the memory is stored in DNA, this is just another version. But this will work even if memory is stored by alternate methods. Further, I can see it working for paternal memory as well.

We know memory can be transferred biochemically, since butterflies and moths from a chrysalis retain memory of things that happened to them as caterpillars, despite the brain essentially dissolving. I can envision a chemical way of doing this by replicating the molecules associated with the memory, or an electrochemical way, essentially replaying the memory into the brain of the developing organism.

This works well with cephalopods (assuming an internal incubation) because males provide a packet of sperm (spermatophore) to the female, and I can envision this being supplemented by a mini brain (of memory only) or memory molecules, so patrilineal and matrilineal memories could potentially be downloaded - perhaps even gender-specific.

If you want limited numbers of offspring, then you could even have maternal brain tissue and paternal memory packets physically passed to offspring, so they actually retain a little piece of the parent containing memories filled with life experiences. This means the parents that die (if we're going with the death model) aren't dying as much as passing themselves along to live in their children.

I have this vision in my mind of maternal memories downloaded and functioning like the cephalopod's own memory, and paternal memory being like a disembodied vision of the paternal parent guiding the young cephalopod along in life with help and instruction. I could even envision a weird sort of post-death romance between cephalopod parents playing out in their children.

Answer 6

Memory symbiont.

Your cephalopods are not intrinsically very intelligent. But they are parasitized by an organism that confers intelligence. This organism resides entirely within the parent cuttlefish. The organism usually reproduces asexually, producing multiple buds and each bud makes its way to an egg. When the egg develops, it has within it a copy of the parental symbiont, and with it all the memories of the parent. The symbiont has no sense of self; intelligence and memory is an emergent property from the union of the two creatures.

The memories in the symbiont do not have perfect fidelity. Older memories might be overwritten and lost, and newer (more relevant) memories are sharper. The new generation are copies of the parent as regards intelligence.

But it is good for life to mix it up. Once in a long while, the symbionts reproduce sexually. It is a strange time for the cuttlefish people. Young are born with a mix of memories from different lineages, and some of these can be very strange, contradictory and sometimes corrupt. Sometimes new energy can come from this hybridiZation. Perhaps during the sexual time, cuttlefish people attempt to infect other tribes of their kind (or maybe even other kinds) with the memory creatures. In adults, a new symbiont infection might drive out the old, taking over the host body for its own lineage. An intelligent noncephalopod which serves as host to a cephalopod intelligence parasite would be an unusual creature to be sure.

Answer 7

In principle, it is certainly possible for learned traits to be passed from mother to child directly. For instance, vertebrates commonly pass information on pathogens they have encountered in their lives down to their offspring via maternal antibodies. While this isn't information that was learned by the brain, this does constitute an evolutionarily widespread mechanism of information transmission directly from parent to child without teaching and with a fairly high bandwidth.

For storytelling purposes, it would certainly be possible to imagine an evolutionary pathway that has, in some animal, led to a system of this kind being coopted into transmitting information from the brain of the parent to the brain of the child (for instance, evolving some in the beginning very limited ability to transmit learned behaviours responding to a disease might be a first step).

Answer 8

Behavioral Epigenetics

The blue-prints for proteins (which give you your physical traits and behaviors) are coded by DNA. The problem is that you don't want to make every protein encoded by your DNA (your liver cells don't want to make the proteins your heart cells need etc.). Also, while sometimes in your life you may want to make certain proteins, other times you may want to "turn off" the DNA codes for those proteins (e.g. the enzymes to digest lactose from your mothers milk is good when you are a baby squirrel but not useful as an adult squirrel). Your body does this via epigenetics, where it "turns on" or "turns off" DNA codes. Whats interesting is that these epigenetic "light switches" can be passed down to offspring.

Lets say you are a rat trying to avoid a predator. If a predator has always had a certain smell for the last million years of rat evolution it would be good if your DNA was permanently coded so that you would recognize that smell easily. But lets say that the smells that mean predators change every few days. It doesn't make sense to get your DNA involved at all - no use increasing cells/blood supply to an area of your brain that detects a certain smell if you won't need to recognize that smell in a few days. BUT lets say that for a few years a certain smell always means a predator is nearby (but then it changes to a different smell for a few more years). You want to recognize that smell easily AND for your children to as well but you don't want it to be permanent because that smell may not be important for your grandchildren.

They did a similar study on rats and showed that fear of a certain smell can be passed down to offspring. Now fear of a specific smell is only a tiny part of your personality/memory but if epigenetics played a much bigger role in the organism then a lot more of the parents personality/memory could be passed down. It also wouldn't need to be permanent - just a starting off point for the organism to then learn whats important in its environment and make new memories. Behavioral Epigenetics is a crazy field and we are learning more and more about what personality traits and "memories" can be passed down.

Answer 9

Its actually possible, but actually not very useful. All the good memory that happened after the conciving of a child- are not there. So all you get is the memory of a thousand childhoods, teenage-angst and the rushed period to adulthood- and a lot of mistakes. All those memorys end, in your parents coitus. And your grandparents coitus.

Family dinners are ankward affairs. In fact, you like to hang out with foreigners more. And the problem is - that there is no real privacy of thougth in this world. So everyone having no children- is quite a little bit suspect. Also some of the people get so nostalgic for the good times, they spend all day sitting on a bench, day-remembering the day away.

Genetic memory was a mistake.