“Memories can be passed down to later generations through genetic switches that allow offspring to inherit the experience of their ancestors, according to new research that may explain how phobias can develop.”
This article explores a study performed on rats that sought to investigate the ability for a species to inherit certain dispositions towards environmental compounds based off the isolated experiences of their parents:
http://www.telegraph.co.uk/science/science-news/10486479/Phobias-may-be-memories-passed-down-in-genes-from-ancestors.html
A link to the study itself:
http://www.nbb.cornell.edu/neurobio/Fetcho/NBBjournalclub/manella.pdf
The study divided mice into two groups, for which each was measured the “odor-potential startle” (OPS) induced by either acetophenone or propanol, compounds for which mice have olfactory receptors. In addition, these groups were given “shock training” during administration of these compounds. Basically, it concludes that the offspring of mice that were conditioned to one of these compounds exhibited a more pronounced reaction (measured by OPS) to that compound, but not to the other.
The authors hypothesize that this phenomenon occurs via a mutation in a particular gene in the DNA that codes for the concerned sensory receptor, thus increasing the offspring’s sensitivity to it.
What this demonstrates conclusively, then, is that environmental stimuli can induce microevolutionary mutations in the quick span of a single generation, in what is a remarkable ability for a species to adapt to a changing environment. However, since the study did not use control groups that were subject to a compound but not to shock training, we cannot conclude to what extent fear was constitutive of the offspring’s reaction to the stimuli.
In light of this, the quote from the news article seems overly optimistic and incorrectly translates the results of the study. Memory itself is a very difficult concept, epistemologically. Heightened perception of an environmental stimulus may be indicative of a sort of trauma, but this is not provable because of the lack of control groups in the study.
Is this indicative of a larger problem of sensational journalism on the part of those responsible for creating publicly digestible presentations of scientific research? Is there indeed something in this study that vindicates the journalist?
While this may stray from the original topic a bit, this concept of heredity of memory through DNA reminded me of another up interesting venue of research examining the remodeling (or mutation) of genomes that goes on at the cellular level via biochemical processes: natural genetic engineering. In a blog post by James A. Shapiro on Huffpost’s Science section (see link below), Shapiro addresses a question posed by James Barham (“…if natural selection cannot explain natural genetic engineering, what can?”). He explains that we don’t exactly know why natural genetic engineering systems have been successfully generating “useful evolutionary novelties in the history of life”, and that despite the fact that molecular biology has provided us with useful mechanisms to explain arrays of sensory, signaling, and decision-making networks in living cells, how these complex molecular networks operate is still unknown to us. I believe that these ideas are very similar to points made in today’s discussion regarding the releases of oxytocin in the brain due to communal interactions; although we can get at some mechanistic understanding of processes at work in memory transference through DNA, natural genetic engineering, or biochemical releases in the brain causing certain sensations/feelings, I think our available knowledge is not enough to pass judgments on the validity of mechanistic or vitalistic explanations for why these operations happen, or what source their progenitor may be.
http://www.huffingtonpost.com/james-a-shapiro/natural-genetic-engineering_b_1511451.html
I agree with the points made that the Telegraph article is using sensational journalism to generate interest in their article. Even when comparing the titles of the article versus the original study, this becomes apparent. “Parental olfactory experience influences behavior and neural structure in subsequent generations” and “Phobias may be memories passed down in genes from ancestors” elicit very different ideas of what the findings suggest. This highlights the importance in evaluating our sources that Prof has been emphasizing all semester.
Despite this, I don’t think this should diminish the implications of such findings. It is obvious that there are many flaws in the design of this experiment, but the results give me hope that in the future the idea of inherited memories could be understood from a genetic standpoint. I would be interested to see studies that examine inherited “memories” that don’t offer obvious evolutionary advantages to offspring. If these could be successfully inherited and studied, it has the potential to mechanistically explain phenomena such as remember past lives and the idea of reincarnation that have only been able to be understood from a vitalistic perspective until now.
This is a very interesting study. The only problem is that this idea that memory is “inherited” seems extremely over sensationalized. Epigenetic memory is nothing too new, as previous studies show how plants have “memory” of duration of seasons in a particular environment that can be passed down to their offspring. In this context, epigenetic changes have biologically occurred in the plants that help their offspring “remember” the length of cold winter, so that they know the right time for flowering, development, seed dispersal, and germination. This occurs through turning off and on different “switches” on genes in their DNA through modification of different histones. This is purely an evolutionary strategy. The study showing this can be found here: http://phys.org/news/2011-07-epigenetic-memory-key-nature-nurture.html.
Other studies have shown “in families where there was a severe food shortage in the grandparents’ generation, the children and grandchildren have a greater risk of cardiovascular disease and diabetes”, which was also inherited through epigenetic memory.
Epigenetic inheritance in response to environmental stimuli provides evolutionary advantage and increases offspring fitness, thus is something that would be selected for. “Memories” how we think of them–fun times with loved ones, going to the beach, playing with out dog, etc– are very different than just a response to stimuli, and remembering these things from our parents would not provide any evolutionary advantage. Thus, while this study is interesting, I don’t think it intends to make us believe we can remember our mother’s first date or our dad’s skiing vacation in the Alps.
I am extremely interested by the possibility of inheriting memory, especially in how it relates to ideas of reincarnation. In the readings about children who remember past lives, the author’s explanation for societies that believe in reincarnation was that at some point they encountered a person who claimed to have memories of a previous life. Yet, if evidence is ever found pointing to the genetic inheritance of memory, then this could point to a better explanation for a society’s belief in reincarnation. If memories can alter DNA then the elders of our society could literally reside within us. Consider primitive tribes that rely on oral traditions to pass on their historical/religious beliefs. The lives of their elders are immortalized and relived through storytelling and tribal ceremonies. Now if we add the notion that these memories are genetically encoded in each member of the tribe, we have a possible origin for reincarnation theory. When you are born you may carry traits in the form of memories, from ancestors that have not breathed for generations. This would be an interesting explanation for the rise of reincarnation beliefs. I understand that there is as of yet little to no evidence for memory based genetic mutation, but the idea is so fascinating that I hope it proves to be true. It would be the first mechanistic evidence for a form of afterlife that I have encountered. The mouse study is limited in its connotations because, as Chiraag observed, it lacked proper controls to distinguish between fear memory and olfactory memory. Perhaps in the future researchers will find evidence connecting the formation of neural networks, with genetic modification.
I wholeheartedly agree with Graham; I had the same thoughts relating the inheritance of memory with reincarnation when this was first brought up in class. While this experiment clearly had flaws, I still think it is a good initiative towards a mechanistic possibility through which vitalistic phenomena such as reincarnation or the remembrance of past lives can be explained. When Chiraag first brought it up, I was personally really excited at the idea.
But as everyone has noticed, the experiment lacks proper controls to verify its claims regarding memory and to call it a potential mechanism through which memory can be stored and passed onto progeny is quite a stretch. An alternative explanation for the mice’s more pronounced reaction could be due to sensitization/desensitization of neurons and action potentials, and the usefulness and affinity of those receptors can be passed on genetically. In this possibility, it is an anatomical advantage (i.e., Darwinism?) that is passed on, not memory. While we are far from associating epigenetic inheritance with memories as we know it, I would like to be optimistic in the possibility.
I recently attended a talk by Terrence Sejnowski titled “What Makes the Human Brain Human?” that talked about some of the same topics of the article. He started the talk by saying he chose that title because it was not technically intimidating and therefore would attract a larger group of people. It was mostly about learning and the development of neural networks, and he mentioned how fear conditioning can induce DNA methyltransferase enzymes affecting the epigenetic memory which is heritable. His interest was mostly in looking at the heredity of things like schizophrenia and Alzheimer’s as a result of these methylation patterns.
The most interesting part of the talk to me was when he talked about the idea of known unknowns and unknown unknowns with epigenetics falling into the former category. The types of discussion or level of skepticism that each category invoked was different. I think when we talk about known unknowns there is a desire to include people, but once you have the interest of a larger group it is hard to adequately explain the background of certain findings or the practical levels of application. The talk did answer the question, but a lot of the evidence would be too much for the average person to understand. Sometimes the type of phrasing needed to capture attention allows certain misconceptions of ideas to become a part of folk knowledge. So for the article I didn’t really think of it as sensational, but I do agree that the way the results were presented was overly simplistic. I think my problem is also with using the word memory just because it evokes a more whimsical feeling to me, but again I think it is an attempt to make the subject seem more relatable and approachable.
I feel that the study still fell well within the limits of mechanism because the trauma the mice were exposed to was a simple physical threat that did not result in death but did result in direct pain and unpleasant emotion. The details of micro-evolution should obviously be looked into further, but it did not seem overly sensational to me to read that certain genes rearrange to adapt to that stimulus, much as in the adaptive immune system, the B-cell’s antibodies rearrange their heavy chain genes in a phenomenon called class switching to better adapt to the antigen at hand. Nonetheless, I find it interesting that across the board of many different spiritual experiences, people associate profound events with strong scents. Personally, the strangest or least mechanistic experiences I’ve had in my life I’ve associated with strong, distinct scents I’d rarely if ever thought I’d smelled before.
I wonder what the results of a more existential phobia would reveal. Could a study like that either help support arguments by children who remember past lives or even diminish them, by showing that phobias can be passed through the family and perhaps olfactory memories could bring suggestion to children who claim to remember details in past lives? If the trauma were, for example, to be less universal, would we see results that defy mechanism?
Kelly, I think the problem that Chiraag is highlighting is that the study did not look at exposure to the scents without fear conditioning so it is impossible to tell whether the genetic modifications are the result of the odor alone or whether the fear proxy played some role in it.