In short, understanding epigenetic tags will change civilization. From many of our previous articles, we understand that DNA is at the core of chromosomes and covered by a sleeve, made out of histone proteins. Triggered by environmental signals, the protein detaches itself from the DNA, enabling section of genetic code to be read by cells; this process is called epigenetic methylation. As soon as the environmental signal is removed, the protein goes back to its previous position and hides the DNA blueprint information.
Epigenetic tags can be considered cellular memory and are acquired through different epigenetic modification mechanisms such as Histone Modification and DNA Methylation. The epigenome learns from its life experiences and interactions with nature. When environmental signals trigger the protein sleeve to detach from DNA, the cells store the information as epigenetic tags, and over time, it creates an epigenetic profile. 
New Discovery: Human Sexuality and Epigenetics
There have been many debates whether human sexual orientation is affected by genetics. For the first time, researchers have found scientific evidence show a correlation with epigenetic mechanisms and homosexuality. Historical data gathered from twin studies and family trees suggested that there might be correlation between human sexuality and epigenetics. Based on the data, when one of identical twins is gay, the other possesses 20% possibility of having the same sexual orientation. Due to this small percentage, it was therefore conceivable that environmental factors played more important roles in human sexuality, than genetics. Furthermore, when an older brother is gay, the younger brother has 33% possibility of being gay, too; this is called older brother effect. 
In the attempt to answer the correlation between genes and environment, particularly in human sexuality issues, a geneticist at UCLA (University of California, Los Angeles), Eric Vilain and his colleagues conducted research to understand epigenetic markers, triggered by environmental signals, which ultimately change genetic expressions without altering the genetic sequence.
Epigenetic markers can be inherited, but are mainly acquired by life experiences.  Research subjects were 37 pairs of identical twins; among them only one twin was gay and 10 pairs were both gay. By scanning those twins’ epigenomes, researchers found five common epi-marks in the gay twins, but not common or not found in their genetically identical straight counterparts. Researchers also created an algorithm to predict sexual orientation of men with a remarkable 67% accuracy.
Eric Vilain says he is not surprised to see that epigenetics is linked to homosexuality. He warns, however, that it is too early to associate these epi-marks with any environmental factors. Further studies will use more twins as research subjects to determine whether the same marks are present. Vilain also acknowledges the limitations in the study. For example, epigenetic markers vary between different tissues in the body, and epigenetic markers found in brain are most likely responsible for sexual orientation. Despite the limitations, many scientists working in the field of human sexuality accept the study as useful addition to the limited information in this specific branch of science.
What We Know …
William Rice, an evolutionary geneticist at UCSB (University of California, Santa Barbara), says, “We already know there is no ‘gay gene’.” He also adds that if there were gay genes, they would have come up in one of many studies that scanned the human genome. To recap, we have known for some time that our sexuality is not due to the sequence of our genes, SO now the race in on to determine what environmental factor cause the genes to express themselves in these natural ways.
This will not be the end of the quest, but it will be a starting point to better understand epigenetic markers and how environmental factors affect the natural expression of ones sexuality.