These adaptive changes are caused by chemical signals in the cells, known as epigenetic tags, which attach to the DNA and tell the cell to either activate or silence a specific gene. “There’s something in the external environment that affects the internal environment, and before you know it a gene is functioning in a different way,” says Yehuda.24 The sequence of the DNA itself doesn’t change, but because of these epigenetic tags, its expression does.
External instead of genetic influences
