Memories of positive associations get written onto DNA
arstechnica.com
arstechnica.com
I feel that many researchers, even geneticists who should know better, still have not internalized the idea that epigenetics is pretty good evidence that somatic DNA is a read/write medium. This leads to sloppy thinking about genetic causes of disease as well as continued persistence of the idea that if we can just collect enough sequences, all genetic causes of disease might be found.
DNA is comprised of four specific nucleic acids which are always the same molecular combination. These acids form into base-pairs which must always be some combination of those four acids.
The DNA itself cannot be 'written to' as if it stores information no less than the following string x = "ACGTACT" can contain additional information beyond those bytes already stored in the string. We could alter the DNA, just as we can alter the string x, but this isn't writing additional data to the binary values, but changing what's stored in those memory locations.
When we're talking about reading/wrting to the DNA, are we actually speaking about modifying the sequence of any given strand, thus "reading/writing to DNA" is a misnomer ? I know there are presently ways to produce DNA synthetically, but what you've said seems to indicate there's room here for any pre-defined sequence I print to end up doing different things in a cloned cell than their synthetic duplicates might.
[Epigenetics] refers to functionally relevant modifications to the genome that do not involve a change in the nucleotide sequence.
There was an eye opening documentary on the subject produced by BBC Horizon a few years ago: The Ghost in your Genes, http://www.youtube.com/watch?v=ehwFVgQ82ZY
So, these "base modifications" are actually increasing the alphabet size, you have the normal A,T,G,C bases and then a set of modified bases.
>I know there are presently ways to produce DNA synthetically, but what you've said seems to indicate there's room here for any pre-defined sequence I print to end up doing different things in a cloned cell than their synthetic duplicates might.
yes, or they might get modified so they are similar to the sequences already present.
This also implies that it would be much tougher to do a Jurassic Park recreation, because the environment is different. You can't just start from scratch with the DNA.
Or am I misinterpreting?
So (supposing that the results of this study can be generalized), yes, culture ends up imprinted in neuronal DNA, one cell at a time.
Since the imprinting is distributed and varies among the billions of neurons in your head it will not be passed to descendants (which inherit half a cell's worth of DNA).
This points to an almost-paradox in biology, which I call Lamarck's Lemma: There may be evolutionary advantage to being able to pass on acquired traits to one's offspring, and no known physical law that prevents it. Why, therefore, would biology not develop at least some Lamarckian mechanisms, since they could offer fitness in the Darwinian sense?
Answer: there appears to be exactly that. It's an exciting time for genetics.
I believe what you mean to say is "We have been able to observe no correlation between methylation of the nerve cells and methylation of the gametes". Unless you can cite detailed studies supporting this null hypothesis. My understanding is that we have no idea.
I would propose that it is possible that some animal "instincts" are really inherited memories from their ancestors.
And that if we look hard enough and deep enough, we may find similar human "instincts".
Have you ever seen a baby with a fear of spiders? Whose parents swear the child has never even seen a spider before?
I think that's pretty testable, just find a way to condition the ancestors and see if the conditioning shows up in the offspring.
The hypothesis is so unlikely given what we know about the brain and reproduction that we'll assume false by default for all memories. Thus the onus is on the experimenter to provide a positive result for some case and also demonstrate that there isn't something else going on.
May we not suspect that the vague but very real fears of children, which are quite independent of experience, are the inherited effects of real dangers and abject superstitions during ancient savage times? - Charles Darwin, A Biographical Sketch of an Infant (1877)
2. Darwin was not infallible. We pick our scientific heroes because of their ability to advance science, to see farther than others, and be remarkably right given the information they had. Our heroes were still wrong about a lot of things, both outside there areas of expertise and inside their areas of expertise. For instance, Newton was the foremost expert on light of the day, and advanced our understanding of optics greatly, but he thought it was a particle. He was wrong, and we do him no honor by believing it a particle in his name.
Plenty of room for spider fears and bird songs.
Apparently the word "memory" is unsettling to some, but it still seems appropriate to me.
If DNA can grow 10,000 different regions of a brain, why is it unreasonable to think that it could also pre-populate some of those regions with patterns that we can access as memory?
Do you mean he's wrong because light is a particle and a wave[1]?
[1] https://en.wikipedia.org/wiki/Wave%E2%80%93particle_duality
It would probably be better to say "just a particle and not a also a wave".
saalweacher has started to cover why, but I'd like to emphasize a request: never ask this question sincerely again.
Darwin is a reasonably valid authority, but it's not because he's "scientific". People are not scientific. Processes are scientific. People who enact scientific processes are scientists. Conclusions drawn from scientific processes are science. "Scientific" should never refer to people.
I think you and Darwin are probably right. That's a long, long, long way from being proven right, though, and it's a huge mistake to assume so from a bit of poetry that Darwin speculated with.
An opinion doesn't turn into a scientific proposition because it matches the speculation of someone who also did significant scientific work.
The whole point of science is that it is method, independent of who is doing it.
"Surely these things would offer greater Darwinian fitness" is as basic a mistake as "Surely we can figure out whether this program will halt without running it".
EDIT: In fact, as I think about it, there is a deep connection between the thought "Knowing the genes of this organism, we may predict its fitness" and "Knowing the instructions of this program, we may predict its halting". I'd love to see a paper on that.
And then, this "smooth path" idea relates neatly with topological notions of computability.
Evolution is much the same, but most people are worse at it because they make the mistake of prioritizing human-values as evolutionary advantages for all species.
For example, cows get slaughtered by the billion by humans. But they're an evolutionary success story from a Darwinian perspective: by being easy to domesticate by early tribes and delicious, they've proliferated far beyond anything which would've happened un-aided by humans.
Of course, there are simple and trivial programs that can be specifically analyzed, but we're definitely not to that level on any of the stuff under discussion here. The analogy really is pretty apt.
But that's the nature of the problem: you know it halts because just executed it till it halts.
while(i>0) { i * 2; }
Turing proved that for some programs there is nothing we can do but run them and see. That doesn't mean that's all we can ever do.
Lamarckian and Darwinian evolution were debated and Darwin won. Lamarck's Lemma, which is a term I made up, points out that, were a random walk to create a mechanism for Lamarckian evolution, Darwinian evolution might well keep it around, as it could offer fitness.
That's why I phrase it as a lemma on Darwin's theory: even if it proves true, as epigenetics suggests, it doesn't make Lamarckian thinking correct. If anything, the opposite: it shows that Lamarckian effects can be explained through natural selection.
Plants can of course move, the classic example being the sensitive plant. Whether or not non-human animals can "talk" depends, basically, on whether one means "signalling" or "language proper". The bee dance can give arbitrarily complex instructions in one particular domain: there is no 'one' bee dance, each performance is roughly as unique as a sentence or so of text.
there is at least one animal that we know is able to talk, at least in our definition of "talk" - this animal is humans, so the Evolution did produce a talking animal.
It is a fallacy to assume that evolution is linear, and that it progresses toward some sort of universal optimum. There is no universal optimum. There are only specific, local optima.
A good example is the megalodon. From all we know, the megalodon was basically a massive, faster, more badass, more ferocious version of the great white shark. Why did the megalodon die out, and the lines that led to the great white survive? Surely big-badassedness is a desirable quality in an apex predator like a shark, right? Well, not really, because circumstances changed. Ocean temperatures changed, prey got scarcer and smaller, and eventually, size became a detriment. Megalodon was too big not to fail. What fit one day no longer fit the next.
The same thing may happen to humans someday, and some other animal may step up to take our places. It seems unlikely, but nature is the one doing the "selecting" in natural selection -- not us. Environments and circumstances change, and as they change, so do the criteria that "fit" the new context. In the Darwinian sense, "fit" refers to suitability to a habitat; it does not refer to "fitness" in the modern sense of the word. Think "product/market fit," not "physically fit."
Not necessarily for plants. They do in fact move. They just do it differently. They have no problem spreading their DNA throughout the world via seeds and pollen. They use a lot less energy too, compared with sprouting legs and getting up to walk around. If they did this, they would likely require much greater quantities of food, including protein, which would put plants at a disadvantage.
In any case, plants have also evolved on a completely different fitness track than that of animals. Plants have evolved incredible manipulation of chemistry, far beyond what humans can produce today, let alone even understand.
I recently finished reading Botany of Desire (Michael Pollan) where he describes how plants have co-evolved with humans, appealing to our selection of flowers, fruits, and vegetables to further distribute their DNA. Who's actually farming who? Interesting stuff.
this is why we have live organisms that able to move - it is called animals, and we have animals that can talk, and we'll possibly have [some milleniums later] animals that are able to efficiently transfer memory through DNA (possibly after these animals become able to calculate and select what memories they'd like to encode into their own DNAs and what of these memories they want to transfer to the offsprings)... Evolution isn't finished as of today, it is possibly only starting :)
The most obvious example of this is humans, who have minimal (if any) genetic advantage over cave-men. I suspect we can find simmilar instances in other species.
It doesn't seem fair to jump to the conclusion that the memory is actually encoded in the methylation pattern somehow. Based on a skim of the paper, the researchers don't seem to claim this either.
Modification of gene expression of genes associated with memory (in the form of changes to neuronal toplogy and excitation thresholds) seems like a more mundane and reasonable explanation.
We can conceivably find an imaging technique that would let us 3D snapshot a brain and all it's connections. But its a big step from that big step down to getting nanoscopic views of the chemistry in every cell.
:-D