Catholic teaching recognizes and accepts the importance of respect for the findings of science – both natural science, and social science. This is why we have in the Vatican a Pontifical Academy for Science, and another for Natural Science.
In moral decision taking, the church also emphasises the primacy of conscience (providing that it is “well-formed”). The Pope’s own theologian to the papal household has described formation of conscience as a process that includes the application of reason, taking all factors into account. “All factors” must surely include those findings of science, but the two Pontifical Academies do not appear to have published anything related to the scientific understanding of sexuality or gender.
For lesbian, gay and transgendered Catholics, these findings are of the utmost importance. For sound moral decisions in our own lives, we need to understand what science has to say on the matter.
From social anthropology we know that in every society, a small but significant minority of people are attracted to the same sex. We also know that there is no universally valid definition of marriage. What differed between societies, was just their social response to same-sex relationships, and to marriage. History shows that even in the Christian church, the understanding of marriage has not always been the same – and for several centuries in the early church, liturgical rites existed for the blessing of same-sex unions.
Other societies differ. Just as some have institutionalized polygamous marriage, some have institutionalized different forms of same-sex relationships. Not all see gender as consisting only of male and female – some have recognized the existence of three or even more genders. All societies recognize the existence of distinct forms of gender roles and expression appropriate for each gender – but just what those roles and expressions are thought to be, differs widely between societies.
Just as forms of same-sex relationships are known from every human society, the same is true in the animal world. Examples of same-sex intercourse have been observed and described for science, from every branch of the animal kingdom. The evidence from science is that sexual activity among animals is simply not exclusively between opposite-sex couples, for the purposes of procreation. In addition to intercourse between individuals of the same sex, numerous examples of non-procreative sex observed between opposite-sex individuals, as well as solitary sex (masturbation).
The study of human physiology has shown that there is an observable physiological basis for the existence of both people with an attraction to the same sex, and for gender variance