
Inherited Learning? It Happens, but How Is Uncertain - cbkeller
https://www.quantamagazine.org/inherited-learning-it-happens-but-how-is-uncertain-20191016
======
klmr
Nick is a former colleague, and I’ve co-authored one of the relevant papers
with Isabelle, and with the greatest respect to the two of them I need to
caution anybody against taking away the wrong message from this misleading
article: _these findings are fundamentally not translatable to humans_ — and
even in most cases to mammals, research in mice notwithstanding.

Furthermore, most, if not all, transgenerational effects of epigenetic
inheritance even in _C. elegans_ is transient. Meaning, the effect attenuates
over just a few generations and then vanishes completely.

To be absolutely clear: Learning is _not_ inherited in humans. There are good
reasons to make this a categorical statement. What’s called “learning” in _C.
elegans_ is completely different from “learning” in humans, and adaptive
changes in mouse behaviour are, so far, still not clearly demonstrated to be
caused by epigenetics, and there are good reasons to be sceptical, as
summarised by Kevin Mitchell: [http://www.wiringthebrain.com/2013/01/the-
trouble-with-epige...](http://www.wiringthebrain.com/2013/01/the-trouble-with-
epigenetics-part-2.html), and by Bernhard Horsthemke:
[https://www.nature.com/articles/s41467-018-05445-5](https://www.nature.com/articles/s41467-018-05445-5)

~~~
SCHiM
Isn't there a similar mechanism in humans though? Like this:

[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6127768/](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6127768/)

""" One the most provocative observations regarding Holocaust offspring was
the report that Yom Kippur war veterans were more likely to develop
post‐traumatic stress disorder (PTSD) in response to combat if they had a
Holocaust survivor parent25. A higher prevalence of PTSD, mood and anxiety
disorders was also observed in Holocaust offspring, largely selected from a
convenience sample of people seeking treatment for Holocaust‐related problems,
compared with controls26. These findings were replicated in a study assessing
the relationship between PTSD in offspring and their own parents, assessed
directly by clinical interview of the parent (s)27. """

~~~
gjm11
Here are some mechanisms by which that could be true without any sort of
biologically-inherited learning being involved.

1\. "Holocaust offspring" may have been told by their parents about their
experiences, and that could sensitize them in various ways (e.g. more
inclination to envisage very bad worst cases; vivid examples of terrible
things available to their imaginations; some sort of unconscious fear of
losing their parents; feelings of guilt at being upset about something less
bad than what their parents went through).

2\. "Holocaust offspring" are, necessarily, offspring of people who _survived_
the Holocaust. Those people might be different genetically from the population
at large, in all sorts of ways. Maybe some of them happen to correlate with
greater susceptibility to PTSD.

3\. "Holocaust offspring" might have a greater tendency to put themselves into
the sort of situations that produce PTSD. (Either for #1-like reasons -- e.g.,
their parents' example makes them feel a greater obligation to put themselves
into danger if they think it may save others -- or for #2-like reasons --
e.g., maybe people who survived the Holocaust tend to be braver or show more
initiative or something like that.)

And a couple of other reasons to be cautious about interpreting these
findings.

4\. "largely selected from a convenience sample of people seeking treatment
for Holocaust-related problems". That seems like an extremely fruitful source
of selection bias.

5\. PTSD is a thing that has to be diagnosed. The people making the diagnosis
know their patients' history, or ought to. It's possible that a psychologist
may be more inclined to diagnose PTSD if they know that their patient is the
child of a Holocaust survivor.

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SuoDuanDao
No mention of Dr. Sheldrake's work on the matter, pity. I wonder whether his
work will be considered mainstream in my lifetime.

~~~
klmr
Rupert Sheldrake is an esoteric quack and pseudoscientist. He has not done any
relevant work in this field, and his theoretical claims are fundamentally
unsound.

~~~
SuoDuanDao
His early work on rates of learning in birds is definitely relevant if one is
agnostic about its legitimacy. What do you consider unsound about his theory?

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hi41
East Asian men are known to add belly fat. This is a cause for concern because
it raises risk for cardiovascular diseases. It is said that this is happening
because of famines causing cells to store more fat so that the human can
survive no-food scenarios. Is this epi generics? Is it really true?

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Guthur
Totally random. I was thinking of this exact scenario on the way to work
today. Not my field, just thought that there seemed to be a growing body of
evidence that parental environment was having significant effects on offspring
and this further scenario seemed some what logic.

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juskrey
Learning, usually depicted as some tedious process, may in reality result to
just some one simple bifurcation triggered by some environmental properties,
which of course can be encoded in DNA, why not.

~~~
klmr
Sure, and that happens all the time _in unicellular organisms_. But it’s
fundamentally different in multicellular organisms because they have distinct
cells forming the _germ line_. So any (random) changes to DNA in other cells
won’t be transmitted. And while mutations in the germ line _do_ happen, they
are also random. So far there’s no known mechanism for systematic, guided DNA
changes, and no good reason to assume that such mechanisms exist (on the
contrary). Furthermore, the article is discussing _epigenetic_ changes which,
by definition, are _not_ encoded in DNA and are instead transient (and thus
not inherited trans-generationally).

~~~
cbkeller
> and thus not inherited trans-generationally

I'm not sure what you're referring to here? There appears to be quite a
significant body of literature on epigenetic inheritance -- just to pick a
few: [1,2,3,4]. The term "Transgenerational epigenetic inheritance" even has
its own wikipedia page:
[https://en.wikipedia.org/wiki/Transgenerational_epigenetic_i...](https://en.wikipedia.org/wiki/Transgenerational_epigenetic_inheritance)

[1]
[https://www.nature.com/articles/ng1199_314](https://www.nature.com/articles/ng1199_314)

[2]
[https://www.nature.com/articles/nrg1834](https://www.nature.com/articles/nrg1834)

[3]
[https://www.nature.com/articles/nature05917](https://www.nature.com/articles/nature05917)

[4]
[https://doi.org/10.1016/j.cell.2014.02.045](https://doi.org/10.1016/j.cell.2014.02.045)

~~~
klmr
Yes, I’m well aware of TEI, it being my former field of research. However, as
your link (4) shows there are all kinds of caveats, and _usual_ epigenetic
inheritance isn’t transgenerational (in fact, it’s a ubiquitous, “mundane”
biological mechanism to maintain cellular state). Your first example — agouti
mouse coat colour — is essentially the only firmly established example of TEI
in mammals. And, as I explained in another comment, TEI tends to attenuate
over generations, and it probably functions very differently in non-mammalian
organisms. To date, the existence of pervasive TEI in mammals remains a point
of contention. Outside of the agouti locus there’s almost no high-quality,
replicated evidence for its existence, and the hypothesis is fundamentally
hindered by the lack of a plausible mechanism [1]. Most epigenetics research
focuses on other things, and there’s general scepticism that TEI in mammals is
all that important [2].

[1] [https://www.theguardian.com/science/sifting-the-
evidence/201...](https://www.theguardian.com/science/sifting-the-
evidence/2016/mar/02/rats-epigenetics-maybe-our-great-grandmothers-arent-
responsible-for-our-alcoholism-after-all)

[2]
[https://twitter.com/ewanbirney/status/1014494822525296640](https://twitter.com/ewanbirney/status/1014494822525296640)

~~~
cbkeller
Ok, thanks for clarifying! Is that part of why you got out of the field?

~~~
klmr
It was a reason, yes. But more generally I started a new job at the time (~ 2
years ago) that took me out of biological research altogether for the moment.

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carlsborg
How do wasps learn how to build those honeycomb structures that make up their
nests. If a wasp is brought up in isolation and is able to do this, clearly
its inherited.

~~~
sacrificedcapon
That's the inheritance of instinct rather than the inheritance of learning. If
one generation of wasp colony "learned" that building their structures under
blue canopy was good (researchers protected these structures) and red canopy
was bad (researchers destroy these structures each time wasps make them ) and
you take the offspring of this colony and raise them in isolation and they
still build under blue canopy and avoid the red canopy, then you can perhaps
say "learning" was inherited.

It's like how infants inherit the instinct to cry and suckle. Inheritance of
learning would be if the mother (since childhood ) was taught to wink and
she'd get more attention and food/milk and her infant winked at her instead of
crying when the infant wanted attention.

~~~
abathur
This is a good response.

Building a little (but speculatively... I don't know much about wasps and
their nest-building instincts): I often wonder what (if any) fractions of
behavior that gets chalked up to "instinct" are actually the result of some
biological/mechanical affordance, normal learning, and reasoning.

(I don't mean to deny instinct as such, but I guess I feel like the razor
should exclude it until it's the only option left?)

To use the hexagonal example, the term "instinct" implies that the creature
_could_ do this thing in a variety of ways, but doesn't. But it wouldn't quite
be "instinct" in the sense we mean it if the hexagonal structure is just a
coincidental emergent byproduct of some detail of the species' visual system,
physiology, etc.

~~~
jerf
Even in humans, which are relatively short on instincts as animals go, you can
see cases where the "instinct" and the "behavior" are not the same thing.
Humans have a suckling instinct, which allows us to drink at birth. But it's
not an instinct that says "ok, here's how human reproduction works, and here's
how milk is produced, and you need to drink from things that look like this
and then when you do these things, your hunger will be slaked"; it's an
instinct that says when you are tickled here in this manner, turn a bit and
start some muscle contractions which result in sucking. They don't cry to say
"hey, I need to suckle"... they cry because they feel bad. They don't know
"understand" the bad feelings or know how to make them go away. But a
combination of a few basic instincts and the environment combine over time to
teach them how to eat for the first time.

Many other animals have much more complicated instincts, but even then you can
often see the instinct starts as something very simple. A fawn "knows how to
walk" at birth, but, look at video of a fawn at birth. I say it's a lot more
like "a fawn knows to recognize it is falling and trigger an only-modestly
complicated reaction to stab the closest leg out in that direction", a neural
circuit so simple with a bit of effort you could almost assemble it by hand in
some sense. A little bit of control circuitry on top gives it a small amount
of mobility.

I think one of the reasons "nervous systems" are so evolutionarily successful
is that they do give that mechanism to go from simple instinct to a much
richer learned behavior, and it's obviously a combination of many things to
get to that point. It's amazing how some of these things work on not
necessarily all that many "instincts".

------
thewhitetulip
I've seen domestic cats getting repelled by any object looking like a snake if
you bring it sufficiently close to it and that too suddenly.

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karmakaze
I'm sure there's lots of research being done in these areas but I was always
bothered by how behaviors are learned or just instinct. What the hell is
instinct? A priori knowledge or just selected, random hard-wiring? I hope we
make some progress during my lifetime and start scratching surfaces of these
mechanisms. I just hope it doesn't turn out to be via gut microbes--I want it
to be digitally encoded.

