A person’s experiences and environment have consequences on their lifestyle, behaviour and body. Scientists even say that our children can inherit these experiences, or our history. Our author Decho from Bulgaria sets out on a journey through the field of epigenetics to check: Do we really “inherit” history?
“Like Father, Like son”
Although it may sound odd, a connection between biology and history is possible, yet highly contestable in the field of science. The so-called field of epigenetics tries to find out how our genes “interact” with the environment. However, many scientists remain sceptical that epigenetic changes pass on from parent to child. So is  there such an interaction at all?
Let’s look at a case – maybe a more personal one. Some years ago, when I found my great grandfather’s high school diploma, I discovered his broad knowledge of languages. This strongly reminded me of my own passion for languages – English, German and Japanese (despite the fact that I began to speak later than most children). Back then, my great-grandfather knew Russian, English, German and Turkish; my grandmother was talented in French and my mother in Spanish.
Realising all this, I thought: “Is it only a coincidence?” In this article, I will try to “dissect” such coincidences with some scientific background. Accompanied  by  historical examples , I will take a closer look at epigenetic changes and how they define a human’s genes. Perhaps I may discover a connection between my  history and my genes.
Between History and Genes
Photo: Menno Huizinga, NIOD Institute for War, Holocaust and Genocide Studies, Wikimedia Commons, commons.wikimedia.org/wiki/File:BC856_HUI-2050.jpg, public domain
What turns epigenetic changes on are diet disorders, specifically famine. Among scientists, a perfect example of this is the so-called Dutch Hunger Winter 1944-1945 during the Second World War. At that time, Nazi Germany blocked food supplies to the Netherlands as a punishment for a national railway strike that aimed to support the Allies’ liberation efforts. Children born during that period had higher risks of obesity, LDL cholesterol, diabetes and schizophrenia. The reason for that is the PIM3 gene, associated with burning the calories in the body, being silenced by a methyl group. In a few words, the Dutch famine made the bodies spare their energy, which set a “trend” for future  generations
Another popular example from the area has to do with nurture. An experiment found out that mother rats which spend more time looking after their pups bring up calm adult rats. However, others do not, so the pups grow up more shy and cowardly.
Epigenetics: How Does it all Happen?
Epigenetic mechanisms: affected by several factors and processes including development in utero and in childhood, environmental chemicals, drugs and pharmaceuticals, aging, and diet. (Photo: National Institutes of Health, Wikimedia Commons, commons.wikimedia.org/wiki/File:Epigenetic_mechanisms.png , public domain)
Epigenetic changes activate or deactivate some specific genes. The activation/ deactivation happens via the so-called histones and chemical tags. Imagine the gene as a ball, the histone as a rope and a chemical tag as a switch. Whenever an epigenetic change occurs, this triggers the switch and the rope either tightens (the gene is less active) or loosens (the gene is more active). This means a given gene may be suppressed – it will transcribe less and make fewer proteins. Or it may be activated – then we have more from this protein. A protein defines the characteristics of a cell. So, epigenetics does not directly influence DNA, but rather “over” it (“epi” in Greek means “over”). All chemical tags of a genome for a given cell are “epigenomes”.
The most popular example of such a chemical tag is the methyl group which usually silences genes. So, if we come back to the Hunger Winter case, PIM3 being methylated means there is less of the protein it makes – therefore slower calorie burning.
Epigenetic changes survive cell division, so such a change may last a lifetime. However, here comes an unsure factor – when egg and sperm cells are formed, most epigenetic changes are erased. So, is the next generation really inheriting these changes in the end?
What Does that Mean in Reality?
Photo: Tomasz Sienicki, Wikimedia Commons, wikipedia.org/wiki/File:Papierosa_1_ubt_0069.jpeg , Creative Commons Attribution-Share Alike 3.0 Unported)
A recent study found out that some changes stay and affect the embryo. It is hence clear that stress or malnutrition heavily hinder the development and good health of the offspring. Or drugs like nicotine – such “poisons” also trigger epigenetic changes that may be passed on to both the egg and the sperm cell. Meaning: Women should not smoke, but men should not either.
Apparently, the choices our ancestors made in their lives shape the way we are.
Still More to Discover in Epigenetics
At the end of the day, epigenetics remains an interesting topic highly contested in the field of science. If we recall the Dutch famine case, many scientists argued that methylation was really inherited, as blood consists of many types of cells and each one with its own epigenome. Moreover, the famine may have led to numerous miscarriages and the survivors had a variant of a gene that made them more resilient. Thus, they just had a specific epigenetic pattern.
I still don’t understand how language knowledge has been a family trait for a century – perhaps it was my family environment that predisposed the next generation to be more curious about it?
The field is developing rapidly and there is still more to expect from it. Nonetheless, the best option for all people, interested in biology or not, is to try to lead a healthy and balanced diet, engage in physical activity after a stressful day. Giving up a bad habit can influence your epigenome. In this sense, you can change the course of your history – and maybe that of the next generations.
