Scientists taught white mice to fear the smell of cherry blossoms.
(“So Bob, what line of work are you in?” “I frighten mice, like my Father and Grandfather before me..”)
The offspring of these frightened mice were never subjected to this cherry blossom trauma but mysteriously, they also feared the smell. More amazing still, the grandchild generation of the original trauma mice, also never subjected to the treatment, reacted with fear.
This is the classic cited example of Epigenetics or Soft Inheritance. The traumatic experience memory is passed along not by DNA, but by methylation changes on the DNA. It’s the DNA equivalent of working memory between generations.
In the old synthetic theory, without soft inheritance:
Two squirrels are living at the same time, in the way, way back when. Along comes a saber-tooth cat. Both squirrels run but the faster one survives and the slower one doesn’t.
Ergo->Faster squirrel genes move one step forward and thanks for playing, slower squirrel genes!
And now, with epigenetics:
Same time, way, way back when. Two squirrels again, different scenario. One squirrel has a close encounter with the saber-tooth cat and gets away, badly shaken but alive. The other squirrel was obliviously examining his nuts in a tree nearby. He never saw the cat, and he is unaffected. Squirrel number 1 has babies and they are born with a fear of cats or at least an extra sensitivity to “something moved!” Squirrel number 1 has enhanced his reproductive status by communicating a mission-critical message to the next generation and the one after. They are literally BORN with more “street smarts” than squirrel number 2’s offspring.
What does it mean if a creature inherits some of the important EXPERIENCES of at least two generations of its ancestors and possibly more? This breakthrough model is fascinating because it describes a form of parental teaching of life lessons to the young in species that can’t archive data or tell stories. Instead, they attach a little chemical post-it note to their genes saying “Beware of Cat”.
If asked “how could the genes know “Cat”? I’d answer “The same way they knew about cherry blossoms.” It’s staggering to think of the sophisticated mechanisms involved and questions rise like mountains in the near distance. Actually, it’s one question, repeated.
1. Something terrifying happens and a sort of snapshot of the event is taken within the organism. How?
2. Which captures details of the experience. How?
3. Ranking some as meaningful. How?
4. And retaining them. How?
5. Ultimately initiating a process that hands this information off to the sex cells for the next generation. How?
6. This new generation “knows” this life lesson as if they’d lived it themselves. But How?
We have now reached the “Talking out of my ass” section.
The thing that gives me shivers (of excitement) is the list of things that must take place for this to work.
- There’s got to be a threshold of some kind. How intense does the experience need to be to “make the cut”?
- There must be a mechanism that takes these “Must know” memories out from all the other memories and decides to engrave them on gametes.
- There must be some crazy-ass coding that allows methylation changes on DNA to communicate details like the smell of cherry blossoms. That would be a highly specific molecule banging into the olfactory brain possibly for the first time ever, and setting off the fire alarm…through code.
- Also, the code is obviously not a complete memory falsifying the experience of the animal receiving it, but close enough that when the real world and this knowledge construct line up, it causes an autonomic emergency deja vu.
I think the “Camera” that could take that memory snapshot is perception/working-memory and the developing chemicals would be concentrations of fight or flight stress hormones that “develop and burn-in” the image. It could also be triggered by something less obvious, like the moment of relief at reaching safety, with the adrenaline fading and your little squirrel heart going like mad. That could prompt a rewind and transcription of the last minute of memory. Who the hell knows?
2, 3 & 4. I imagine the salient details are the Bold and Italic sensations of that experience, the ones that loom and glow in memory as you look back on it, momentarily experienced again. Long term memory is the most economical way to retain this information and would occur naturally. Perhaps mentally reliving the event (including within dreams) a critical number of times prioritizes passing it forward.
5. I got nothing.
It seems certain to me that many classic human knee-jerk fears like spiders, toadstools and snakes are among our deeply reinforced examples of this process. And that brings up some issues closer to home. Presumably, every human baby is born with some of these “presets”. It seems like the nearly global ones must become default elements of our standard inheritance. Is there some process that triggers the elevation of a methylation memory to DNA proper? Is there some tipping point of reinforcement that causes that? Like if PARENT has a trauma experience coded and CHILD does too, (as their own direct experience, not passively) would the two copies being present in CHILD pass on the message to GRANDCHILD with more urgency? For example, could two doubly reinforced people merging their four copies at the moment of conception cause a crossover to DNA inheritance? That question is kind of rhetorical, I’m just shaking my head at the amazing possibilities of this system.
Other random questions:
- Could that kind of double reinforcement play a part in paralyzing phobias?
- How long does it take from trauma to rewritten gametes? If the survivor conceived the next day would the information be ready?
- Men replenish sperm at a rate that shows tremendous optimism, and a woman’s eggs are more or less archived, or at least they travel like a slow and stately parade in comparison to sperm. Does this mean these memories are sex-linked?
- Since our gametes are so different would there have to be separate mechanisms to do the encoding? Do eggs get these “critical updates”?
- Are there equivalent positive messages about life success, not just skin-of-our-teeth escapes? It makes some sense to me that success heuristics belong in the system too, but would be harder for us to demonstrate experimentally. Perhaps that’s more of a learn by observation thing. Animal parents can demonstrate life skills but can’t demonstrate how to avoid a monster attack.
- Can these messages be annotated in the trip from say, a grandparent to a grandchild?
- Could separate, different messages from different parents ever blend and synthesize into something unique?
- Is there a decay time for these messages? Do they fade across generations if not reinforced? Is there a mechanism protecting normal healthy species behavior from being dangerously rewritten or overridden by these alerts?
In summary, we are talking about an evolutionary mechanism which fills a couple of the gaping holes in Darwinian theory.
A Tautology for a Theory: “Survival of the fittest” is a fugue idea, chasing its tail. The fittest can only be described by their survival. The Darwinian mechanism is really about the elimination of gene-pool competitors leaving “the fittest” still standing and reproducing. Kinky!
Time: There is no mechanism for the fittest to develop their adaptive advantage except endless friggin’ time and lucky mutations. Evolution has happened much faster in reality than jives with Darwin’s crawlingly slow “change through random accident and mutation” story. Instantly this makes much more sense than calling upon eternity to explain your mechanism.
Random Changes: Random mutations have been studied constantly since the theory launched. In an experiment replicated many times, random mutations have been generated in thousands of generations of fruit flies in the lab by radiation. Not a single lucky mutation resulted. No change in that population resulted.
Galapagos finches have fitness-enhancing beaks but no practical way to acquire them. Deprived of support from randomness and eternity, Darwin is an empty lab coat. We have reached a happy upgrade to our thinking.
Evolution is sophisticated, multilayered and complex. It stacks the deck in any way it can. It behaves at the very least, as if strategic. We are arriving at theories that mirror the subtlety of reality. We are finally getting better at this.