Part 1: Is This a Revolution?
1 The power of context
2 DNA doesn't work that way
3 Development, Cell-Context Interactions
4 What is DNA?
5 Deep Dive: DNA
6 Control, turning the switch on or off
7 Deep Dive: Regulation

Part 2: Basic Concepts of Epigenetics
8 Epigenetics that Change Body and Behavior
9 Deep Dive: Epigenetics
10 How Experiences Change the Brain
11 Deep Dive: Experience
12 Primate Studies
13 The Science of Memory
14 Deep Dive: Memory
15 We are what we eat
16 Deep Dive: Nutrition

The Meaning and Mechanism of the Third Inheritance
17 The effects of epigenetics are inherited.
18 In the sea of ​​diversity
19 Evidence that experience is inherited
20 Grandparent Effect

Part 4: Finding the Hidden Meaning
21 Things to Watch Out For
22 Well-founded Hope
23 Key Lessons from Behavioral Epigenetics

Huzhou

Epigenetics, the hottest topic in biology
Scientifically explaining how experiences are etched into the body and mind.

Epigenetics refers to “the way genetic material is activated or deactivated depending on different contexts or situations.”
In other words, epigenetics affects our bodies and minds by changing the way DNA works without changing the DNA base sequence.
This means that we can change our thoughts, feelings, and behaviors by turning genes on (activating them) or off (silencing them).

The idea that experiences affect both body and mind may not seem like a new idea at first glance.
We accept as "common sense" that stress causes disease, that what we eat directly affects our bodies, and that neglect or abuse in early life negatively impacts our mental health in adulthood.
However, how our experiences actually affect our 'biological states at the molecular level' has been shrouded in mystery.
Epigenetics provides scientific evidence for this process.


According to Robert Sapolsky, a professor of biology and neuroscience at Stanford University, “epigenetics is the hottest topic in biology.”
In fact, in PubMed, a search engine for life science, medicine, and psychology papers under the National Institutes of Health, there were only 46 articles mentioning 'epigenetics' over a period of 36 years from 1964 to 2000.
However, in the first decade of the 21st century, 1,922 articles mentioned epigenetics.
This is more than 40 times the number.
What's even more surprising is that in 2013 alone, 2,413 articles mentioned epigenetics.


The reason research in this field has exploded is because epigenetics actually explains a huge number of phenomena.
For example, “psychosis, memory and learning, depression, cancer, circadian rhythms, obesity and diabetes, autism, trait inheritance, homosexuality, addiction, aging, insect morphology, exercise and nutrition, environmental toxins…” and the list could go on and on.
Because the range of areas of life that can be explained by epigenetics is so diverse, this book focuses on behavioral epigenetics, “the study of how epigenetic effects influence psychological processes such as emotional reactivity, memory and learning, mental health, and behavior.”


What matters is not what genes you are born with.
What genes do

Part 1, "Is This a Revolution?", examines the issues that have sparked such excitement in the field of epigenetics.
First, it is pointed out that epigenetics, which has become a well-established field of biology, has discovered that there are actually things attached to our DNA (epigenetic marks) and that these have a decisive influence on how DNA functions.
In particular, he says, epigenetics has shaken the "nature versus nurture" debate to its core, as it suggests that "experiences and the circumstances we find ourselves in" can influence epigenetic marks (Chapter 1). Epigenetics also overturns our preconceived notion about DNA: genetic determinism, which holds that "our innate genes determine our phenotype (traits or personality)."
The book asserts that DNA cannot create any of our characteristics on its own, and emphasizes that our traits are created through the interaction of 'genetic factors' and 'non-genetic factors'.
Given that the activity of genes varies depending on experience and environment, it's not what DNA you have that matters, but what that DNA does. (Chapter 2)

So how do epigenetic marks regulate DNA? The book provides an accessible overview of the epigenetic mechanisms that silence (DNA methylation) and activate (histone acetylation) genes.
The most representative example is DNA methylation, which is the process in which molecules called methyl groups attach to DNA, similar to how pepper particles sprinkled on a plate of spaghetti attach to the pasta strands (of course, the methyl groups on DNA attach more strongly than the pepper on pasta).
'DNA methylation' is known to mostly silence genes (make them non-functional).
Another epigenetic mechanism occurs when acetyl groups are attached to molecules called "histones," which are the coiled strands of DNA.
Histone acetylation has the opposite effect of DNA methylation, namely, increasing gene expression (function). (Chapter 6)

Experience can turn genes on or off
How on earth?

Part 2, "Basic Concepts of Epigenetics," examines the fundamental theories of behavioral epigenetics, from well-known research cases to a variety of new and cutting-edge experiments.
In particular, Harlow's 'consolation of touch' experiment points out that if early life experiences produce certain outcomes (children who were neglected or abused early in life are more likely to develop mental disorders later in life, or premature babies gain weight, reduce stress, and have less pain response when given massage therapy), it is important to understand 'how' the experience produces those outcomes.
If we understand the principles of how an experience in early life influences us years later, we can create a means of recourse other than persuading parents that they should not abuse or neglect their children.
This chapter details the groundbreaking and most representative study of mother rats by McGill University's Michael Meaney and Moshe Szyf, which revealed the physical effects and consequences of early life experiences. (Chapter 10)

So, are there any studies examining the epigenetic impact of experience on humans (or primates)? The book includes brain studies of suicide victims, revealing that early life experiences are linked to a person's epigenetic state, and blood analysis of rhesus monkeys, demonstrating that dominant sequences can alter DNA methylation status.
In addition, we examine the flood of human blood cell research that has emerged over the years, claiming that blood research has opened up the "possibility" of understanding human epigenetic status (Chapter 12).

Other fascinating stories include the involvement of epigenetic mechanisms in the creation and storage of memories (Chapters 13 and 14), and discussions of the epigenetic influence of nutritional status and eating habits on gene expression (Chapters 15 and 16).
In particular, the fact that 'what a future father consumes' can also influence the characteristics of his children later on is beginning to emerge, making it clear that 'the psychological and biological influences of epigenetics' can be inherited.

Genes imbued with experience are passed down.
How on earth?

Part 3, “The Meaning and Mechanism of Inheritance,” provides evidence to explain how the effects of epigenetics are actually passed down from generation to generation.
Modern biology believes that there is a 'barrier' between our germ cells (sperm and eggs) and our somatic cells (all the rest of our cells) that prevents them from influencing each other, and therefore 'acquired traits cannot be inherited'.
This 'modern synthesis' holds that only genes drive evolutionary change, and that life experiences have no effect on offspring.


However, according to the book, epigenetics is proving that experiences are passed down between generations not only through 'behavior and environment' (Chapters 17 and 18), but even through the 'germline' (Chapter 19).
The book highlights the fact that epigenetic effects are passed down the germ line, with studies showing that the diet of pregnant mice affects the DNA methylation (gene silencing) and fur color of their offspring, and studies examining changes in the female offspring of male mice fed a high-fat diet.

The Swedish study of the Överkalix region (Swedish study), which revealed that the nutritional status of grandparents (and ancestors) is inherited, is the most surprising and interesting section in this book (Chapter 20). The Swedish study was inspired by the Dutch Famine Study, one of the most representative studies in epigenetics.
In the northernmost part of Sweden, Överkalix, there was a record of annual grain harvests from the 19th and 20th centuries.
This data allowed scientist Lars Orlov Bygren and his colleagues to conduct innovative epidemiological studies to determine whether the amount of food available to a given generation was related to the traits of its descendants.
The results of the study are truly astonishing.
This is because the results suggested that 'if a certain male did not have enough food during his slow growth period (ages 9-12), his future son was less likely to die from cardiovascular disease complications.'
This effect was passed down through fathers and grandfathers, and it demonstrates that 'epigenetic effects are passed down the germ line', as their grandchildren were not present at all, either as embryos or as primordial germ cells, at the time they overate or starved.

Things to be wary of as the weather heats up, yet there are still hopeful things.

Part 4, "Finding Hidden Meaning," examines the limitations and hopeful lessons of epigenetics.
First, he points out that although epigenetics is "hot and promising," there is still much to be discovered, so we should not blindly trust it (Chapter 21). He says that it is dangerous to be so infatuated with the surprising discoveries of behavioral epigenetics that we develop "another form of determinism," such as "epigenetic determinism."
The book points out that while some studies on behavioral epigenetics have highlighted the long-term impact of early experiences, this does not necessarily mean that "a baby's early experiences will have a lasting impact on their characteristics."
The author speaks decisively.
“Human development is not a deterministic process,” he says, adding, “It is a false assumption that our fate is in any way completely determined in the early stages of life.” (p. 362) He also points out that it is highly unlikely that epigenetics is the pathway through which our ancestors’ psychological memories are passed on.
Although epigenetic markers reflect certain 'aspects' of our ancestors' history (for example, how much food they ate at a particular time in their lives), it is difficult to believe that our genomes contain specific memories of our ancestors' experiences.

Although limitations remain, the author predicts that the new knowledge about epigenetics that scientists have uncovered so far will have positive and definite effects in various fields in the future (Chapter 22). It can be used as a basis for developing drugs or methods that have a 'therapeutic effect' in cancer, aging, addiction, memory disorders such as Alzheimer's disease and post-traumatic stress disorder, and mental pathologies such as schizophrenia, bipolar disorder, autism, and depression.
In fact, he says, epigenetic drugs have been developed and are being used to treat cancer, and it is highly likely that treatments for memory disorders and depression/anxiety will also be developed in the future.

Key Implications of Behavioral Epigenetics

The astonishing discoveries in epigenetics, which examine how the genome changes depending on environment and context, have overturned dogmas and paradigms in biology. They are dismantling not only the "genetic determinism" that DNA determines human traits, but also the conventional dichotomy of "nature versus nurture."
The belief that experience continuously influences genes also challenges the proposition that 'early experiences determine the future.'
As the book repeatedly emphasizes, “If you want to know how smart a baby will be as an adult, you just have to wait until they do.” This means that even if a dark childhood experience caused post-traumatic stress disorder, future experiences can help alleviate the symptoms.


The implications of epigenetics are incredibly vast and complex, but the message non-scientists can take away from it can be a bit stale.
The author states, “The advice we can glean from the data available today is not so different from the advice we would have heard even if we knew nothing about epigenetics” (p. 423).
Advice such as eating plenty of vegetables, maintaining good social relationships, and avoiding toxins.
The message is that we must care for our children carefully, carefully select and build their environments, and live in ways that promote their health and development.


However, just because the lessons of epigenetics are boring doesn't mean they're meaningless.
The belief that 'experience and environment' are important has a profound impact on how we live our lives and how we treat the people around us.
Epigenetics has important implications for everyone: people debating whether to take up the tedious task of exercising, parents concerned about how to raise their children, doctors trying to understand how drugs work, and politicians seeking ways to keep the public safe from environmental toxins.
Epigenetics is incredibly important to all of us in one way or another.


Now, the saying, “It’s how you live that matters” is no longer just a slogan.
Even in molecular science, this is being proven.
It is, of course, up to us what we choose.