Since the 1970s, according to most polls, Americans have grown steadily more tolerant of pre-marital sex, divorce, birth control, and homosexuality, even as they have grown more and more intolerant of adultery. The trend is so robust that, in 2013, the Atlantic declared marital infidelity to be “America’s last sexual taboo.” It seemed that the norms against most consensual sexual behaviors were being swept aside in the wake of the sexual revolution, but but the norm against defying one’s marriage vows remained as strong as ever.But recent data from the General Social Survey—compiled here by Paul Hemez of Bowling Green State University—raises questions about whether even “the last taboo” is starting to falter. According to Hemez, the share of Americans who said “marital infidelity is always wrong” climbed steadily from 1973 to 2008, but fell back down to 1994 levels in 2015.As would be expected, the survey shows variation by age and education level. Millennials (at 75 percent) are least likely to strongly disapprove of adultery, while Gen-Xers, (at 82 percent) are most likely. People without a high school degree are most conservative, at 85 percent disapproval. People with a college degree or higher are most permissive, with only 73 percent saying that infidelity is always wrong.To be clear, there is not nearly enough evidence to think that attitudes towards adultery will follow the trajectory of other sexual taboos. It has for decades stood out as an exception to our culture’s increasingly libertarian attitude toward sexual issues. A Pew poll from last year showed almost no change in attitudes toward extramarital affairs between 2001 and 2015 (although support for polygamy, adultery’s not-so-distant cousin, doubled over the same period).Sexual attitudes can change with extraordinary speed. It seems unlikely that adultery will ever become fully sanctioned and celebrated, but it’s also not impossible that norms against it will break down around the edges, with the expectation of marital monogamy diminished. Here’s hoping that doesn’t come to pass, and that the end of the last taboo isn’t just the last shoe to drop in the sexual revolution.