KNOXVILLE – Epigenetics – how gene expression is regulated by temporary switches, called epi-marks – appears to be a critical and overlooked factor contributing to the long-standing puzzle of why homosexuality occurs.
The short definition in the opening sentence seems to imply that this is something that can happen at any time during an organism’s life cycle, with the further implication that gene expression is something that can therefore be modified at will.
However, this short definition is misleading in the extreme. Even the often misleading (when it comes to anything political/controversial but pretty good when it comes to science) Wikipedia shows that the effect of the switches is something that happens while the organism is developing. In the case of mammals, this would be in utero.