The possibility of human pregnancy hangs on whether there is both male and female genetic material, though not all heterosexual couples can have children [due to diseases, obesity for example], and it shows that lesbian and gay people have chosen their respective paths, they have already eaten the cake, but want to have it too. The cake in that sense is children, you choose not to be heterosexual, but still want to bear children that requires a heterogenous mix.
In fact it has a clear religious leaning, after all what were many of the gods of ancient human history gods of? Fertility.
In fact it has a clear religious leaning, after all what were many of the gods of ancient human history gods of? Fertility.