One of the greatest scientific discoveries in human history has been the discovery of our genetic system, which had long been a mystery. Today, our common sense understanding of science tells us that our genes are controlled by hereditary material called DNA, and DNA, once inherited from parents, cannot be changed for life.

This widely accepted notion, however, has been completely overturned by the study of epigenetics. It is now well known that although the DNA itself does not undergo change, chemical bonding occurs in the DNA due to the changes in mother's uterine environment, which then modifies the expression of genetic information. Because the chemical bonding of DNA differs, very slight differences have been proven even in identical twins.

Even so, this chemical modification of genes occurs prior to birth, and it was thought that the post-birth environment did not affect genes.

According to an article in the American journal "Pediatrics," this conventional wisdom has been overturned by research results.

Telomeres are genetic material located in the four places on the ends of chromosomes, which contain DNA. It is known that when the cells divide, they become shorter. Over time, all somatic cells undergo repeated cell division to regenerate, but the telomeres become shorter with each division, and when they reach a certain length, the somatic cells become unable to divide. Based on this fact, it appears that telomere length is the deciding factor when it comes to longevity.

The article in "Pediatrics" examined how telomere length in children was affected by the experience of paternal absence (through death, divorce, and incarceration). The study interviewed parents of 2,420 children, asking about attributes of the parents and child 48 hours after the birth of their child and subsequently about the home environment at the ages of one, three, and five. Samples of saliva were taken when the children reached the age of nine, and the telomere length of epidermal cells (average amount of TTAGGG sequences per chromosome) in saliva was measured using the genetic methods (details omitted here).

The results were astonishing. The average length of telomeres in children who had experienced the loss of their father before the age of nine was found to be 14% shorter than those of children who had not experienced such a loss. Telomere length also differed according to the cause of father loss: 16% shorter when the cause was death, 10% shorter in the case of incarceration, and 6% shorter in the case of divorce. Furthermore, the decrease in telomere length was 40% greater in boys than in girls, and the rate of telomere shortening related to the serotonin transporter gene that plays a role in depression was also found to be the highest. The shortening mechanism has not been clarified, but the authors infer that it is related to the increase in stress due to father loss.

Research does not yet indicate that high levels of stress lead to a shorter life span, but it is surprising to learn that experiences can result in genetic change (telomere shortening). We are witnessing groundbreaking discoveries at this very moment.

• Mitchell C, McLanahan S, Schnener L, et al. Father loss and child telomere length. Pediatrics 2017 Aug; 140(2).