Morality as set within a culture definitely changes over time.
However, there are moral teaching of scripture that do not change.
Sexual morality and the definition of marriage are certainly issues that the CHURCH must deal with. Whether the worldly sexual mores might inform, but cannot determine right and wrong.
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As you indicate, there is an elephant in the room. In biblical times (and in times before) women were married very soon after being able to conceive. Marriage followed almost immediately. Homosexual practices involved an older man and a young boy. There was little birth control. Children were needed as workers on farm and in the shops, and to take care of theirm parents in old age.
The biggest issues of marriage were adultery and having more than one wife. The morality we deduce from bibliocal letters to the churches and other verses made great sense, and there were few real issues with regard to conclusion that sex was within marriage, for the procreation of children, and between a man and a woman..
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Today, for better or worse, we are in a different place with different issues. We often apply the same sexual conduct as in the early church, resulting in asking our children to be celibate for 12 years or more. Since we cannot support families with a dozen children, we pratice natural or artificial birth control, removing the link between sex and child-bearing. Sex is instead about intimacy and commitment. We no longer use sex as the method to produce workers for our farms and to support us in our old age within the family unit or clan. Homosexual partnerships are not typically between a older man and a young boy, and committed realtionships are at least as likely to continue as heterosexual realtionships.
For me, the largest issue is expecting those between puberty (often at age 10 and marriage to be celibate. Celibacy should be a calling not a man-made rule. Yes, the issue also exists for the unmarried, and particularly those whose spouse has died. Should they be automatically be considered to be called into cel;ibacy or rushed marriage?
We have seen what forced rules of celibacy can do to variuous groups.
The CHURCH and the churches need to face these issues.
Keep in mind that sex in marriage occured to women as young as 12 in Biblical times. Today we say that sex with someone that young is immoral, but if it wasn't the case during the old days, Jesus wouldn't have been born to Mary. So yes, morals do change over time.