A process called METHOLATION can occur at any time in your life to turn on or turn off genes.
The study of this phenomenon is new to science, but homosexuality and a number of other pathologies clearly show signs of the occurrence of metholation.
What you need to look up are the terms EXOGENOUS and METHOLATION.
Interesting.
That may explain some men and women I have known who have done a 180 in middle age, and "embraced" a homosexual identity.
In the case of women, there is even a strange change in physical appearance.