Marriage has been redefined several times over the centuries by preachers professing to be Christians:
Restrictions to female virgins and widows abolished.
Male polygamy abolished as Jewish Biblical marriage was abandoned for Roman pagan cultural marriage.
Race mixing bans became standard doctrine amongst American Baptists and other evangelicals during Golden Age of Christianity. A legacy of which is some American evangelicals, mostly old ones, still believe race mixing is a sin.
Race mixing ban abolished.
Roman Carbolic doctrines banning Biblical exceptions for divorce are adopted.
What next? Will Evangelicals give-in to growing demand for gay marriage?