Is fear inherited? How can that happen?

A new study suggests there is a genetic imprint from traumatic experiences carries through at least two generations. I saw this and was IMMEDIATELY skeptical. Too much remains unanswered and also goes against what we already know.

Fearful memories haunt mouse descendants : Nature News & Comment.

Certain fears can be inherited through the generations, a provocative study of mice reports1. The authors suggest that a similar phenomenon could influence anxiety and addiction in humans. But some researchers are sceptical of the findings because a biological mechanism that explains the phenomenon has not been identified.

Ressler and his colleague Brian Dias opted to study epigenetic inheritance in laboratory mice trained to fear the smell of acetophenone, a chemical the scent of which has been compared to those of cherries and almonds. He and Dias wafted the scent around a small chamber, while giving small electric shocks to male mice. The animals eventually learned to associate the scent with pain, shuddering in the presence of acetophenone even without a shock.

This reaction was passed on to their pups, Dias and Ressler report today in Nature Neuroscience1. Despite never having encountered acetophenone in their lives, the offspring exhibited increased sensitivity when introduced to its smell, shuddering more markedly in its presence compared with the descendants of mice that had been conditioned to be startled by a different smell or that had gone through no such conditioning. A third generation of mice — the ‘grandchildren’ — also inherited this reaction, as did mice conceived through in vitro fertilization with sperm from males sensitized to acetophenone. Similar experiments showed that the response can also be transmitted down from the mother.

The findings are contentious. While the proposal is astounding – one observer called it “the most rigorous and convincing set of studies published to date demonstrating acquired transgenerational epigenetic effects in a laboratory model” – the rest of the community is stumped by the lack of a mechanism for this “memory” to be transmitted. This is important because without a plausible mechanism, some other factor could account for the results. Science is conservative. Skepticism (which is of critical importance in scientific discussions) will continue until the molecular mechanisms can be detailed and that could be a while.

So, file this research as something to watch, not swallow whole right of the bat. This is an extraordinary claim and extraordinary evidence is not there yet.

Here is the paper link: Parental olfactory experience influences behavior and neural structure in subsequent generations : Nature Neuroscience : Nature Publishing Group.[Full view by subscription only]

  8 comments for “Is fear inherited? How can that happen?

  1. Daran
    December 2, 2013 at 10:51 PM

    recently, some research I read showed that DNA is changed “on the fly” so to speak, so this could be true

  2. gewisn
    December 3, 2013 at 12:09 AM

    Some questions that come to mind:
    1) were the people judging the shuddering (or other behavioral responses) blinded to the experimental vs control group? how was reliability established and measured?
    2) was there a condition in which the sensitized parent mouse copulated but the pregnancy was biologically from another mouse, e.g. a sensitized mouse was the apparent father, but the offspring was actually the result of artificial insemination with sperm from a non-sensitized mouse?
    3) how large are the baseline differences of behavioral response to the stimulus in a control pop’n of mice?

    If this pans out, it will be very interesting, indeed.

  3. December 3, 2013 at 1:26 AM

    While you should be skeptical, it has been shown that environmental factors can activate genes, and that activation can be inherited — that is, without actual changes in the gene sequence. I’m not claiming that that’s what is happening in this case, just that environment, and not just your DNA, can influence inherited traits.

    That said, I’m extremely skeptical that fear has either a genetic OR epigenetic basis.

  4. December 3, 2013 at 4:57 AM

    Is the use of the word ‘fear’ correct here? When humans experience fear that is surely in our minds, a part of our consciousness. As mice (as I understand) have not evolved that far, we should surely use a different word to express their reaction to external stimuli.

  5. Brad Worden
    December 3, 2013 at 3:22 PM

    Why? If you have observed animals certainly you can agree fear is not strictly a “human” trait. Fear is a basic animal response.

  6. December 4, 2013 at 3:46 AM

    Yes Brad, I take your point, certainly with all mammals. With animals lower down the evolutionary scale we usually just call it survival instinct. Does this mean that all animals, with brains, have some sort of consciousness? Alternatively it may show that what we regard as our special ‘human consciousness’ is only an illusion.

  7. Paul Fedorchak
    December 9, 2013 at 9:06 PM

    This could be a chance finding (type 1 error), but only time and attempts to replicate will tell. If, via random assignment, Dias and Ressler unfortunately ended up with the mice who naturally reacted more strongly to the target odor being assigned to the conditioned group, that would explain why the next generation, and the next, also showed the reaction. This could also explain all the related physiological “changes.” As Sharon Hill pointed out, this finding would also go against many earlier failed attempts to show the same effect (all the way back to McConnell’s infamous Planaria study).

  8. claudio
    March 21, 2014 at 10:15 AM

    the only BIG problem I see here is how such an information could pass down through sperm (?!) and indeed account for going beyond F2 generation

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