In 1982, the Syrian government besieged the city of Hama, killing tens of thousands of their own citizens in sectarian violence. Four decades later, the rebels used the memory of the massacre to help inspire the demolition of the Assad family that had supervised the operation.
But there is another lasting effect of the attack, hidden deeply in the genes of Syrian families. The grandchildren of the women who were pregnant during the siege, grandchildren who never experienced so much violence, however, they carry marks in their genomes. They enter their mothers, this genetic impression offers the first human evidence of a previously documented phenomenon only in animals: the genetic transmission of stress between generations.
“The idea that trauma and violence can have repercussions on future generations should help people to be more empathic, help policy formulators pay more attention to the problem of violence,” said Connie Mulligan, Ph.D., Professor of Anthropology and the Genetics Institute of the University of Florida and senior author of the new study. “I could even help explain some of the apparently unwavering intergenerational cycles of abuse, poverty and trauma we see throughout the world, even in the United States,”
While our genes do not change due to life experiences, they can be adjusted through a system known as epigenetics. In response to stress or other events, our cells can add small chemical flags to genes that can calm them or alter their behavior. These changes can help us adapt to stressful environments, although the effects are not well understood.
These are revealing chemical flags that Mulligan and his team were searching in the genes of Syrian families. While laboratory experiments have shown that animals can transmit epigenetic stress firms to future generations, which has been the same in people has been almost impossible.
Mulligan worked with Rana Dajani, Ph.D., molecular biologist at the University of Hashemite in Jordan, and anthropologist Catherine Panter-Brick, Ph.D., from Yale University, to carry out the unique study. The investigation was based on following three generations of Syrian immigrants to the country. Some families had lived Hama’s attack before fleeing to Jordan. Other families avoided Hama, but lived the recent civil war against the Assad regime.
The team collected samples of grandmothers and mothers who were pregnant during the two conflicts, as well as their children. This study design meant that there were grandmothers, mothers and children who had experienced violence in different stages of development.
A third group of families had emigrated to Jordan before 1980, avoiding the decades of violence in Syria. These first immigrants served as a crucial control to compare themselves to the families that had experienced the stress of the civil war.
She herself of refugees herself, Dajani worked closely with the refugee community in Jordan to generate confidence and interest in participating in history. Finally, he collected cheeks of 138 people in 48 families.
“Families want their history to be told. They want their experiences to be heard,” said Multigan. “I think we work with every family that was eligible to participate in the study.”
Back in Florida, Mulligan’s laboratory scanned the DNA for epigenetic modifications and sought any relationship with the experience of families.
In the grandchildren of Hama’s survivors, the researchers discovered 14 areas in the genome that had been modified in response to the violence experienced by their grandmothers. These 14 modifications show that stress -induced epigenetic changes can appear in future generations, as can in animals.
The study also discovered 21 epigenetic sites in the genomes of people who had directly experienced violence in Syria. In a third finding, the researchers reported that people exposed to violence, while in their mothers’ uters showed evidence of accelerated epigenetic aging, a type of biological aging that may be associated with the susceptibility to age -related diseases.
Most of these epigenetic changes showed the same pattern after exposure to violence, which suggests a kind of epigenetic response common to stress, one that can not only affect people directly exposed to stress, but also future generations.
“We believe that our work is relevant for many forms of violence, not only refugees. Domestic violence, sexual violence, armed violence: all the different types of violence we have in the United States,” Mulligan said. “We should study it. We should take it more seriously.”
It is not clear what, if anyone affects these epigenetic changes in the lives of the people who carry them within their genomes. But some studies have found a link between epigenetic changes induced by stress and diseases such as diabetes. A famous study of the Dutch survivors of the famine during World War II suggested that their offspring carried epigenetic changes that increased their chances of having overweight later in life. While many of these modifications probably do not have any effect, it is possible that some may affect our health, said Mulligan.
The researchers published their findings, which were supported by the National Science Foundation, on February 27 in the magazine Scientific reports.
While carefully sought evidence of the lasting effects of war and trauma stamped on our genomes, Mulligan and his collaborators were also beaten by the perseverance of the families with whom they worked. His story was much larger than the simply surviving war, Mulligan said.
“In the midst of all this violence, we can still celebrate their extraordinary resistance. They are living satisfactory, productive lives, having children, continuing with traditions. They have persevered,” said Mulligan. “That resilience and perseverance is possibly a unique human feature.”