You do not read much about polygamy these days but a recent Wall Street Journal article on religion raised the question in a provocative way. Rose McDermott, a professor of political science at Brown University, noted that polygamy may be a popular punch line in some movies but “plural marriage is as serious an issue as it’s ever been.” And it is on the rise in the modern West.

One example can be seen across the border, in Canada. A 1890 polygamy law is being tested by groups that insist it violates religious freedom. The core of their argument is that consenting adults have the right to form families in any way they please.

Polygamy is, of course, not new. It has been a common practice for most of human history. Many religions promote it. Muslim practice encourages it and in new Muslim immigrant enclaves in Paris, London and New York the law against it is being challenged. A 2006 report says that 180,000 people were living in polygamous households in France. When the government banned it in 1993 it tried to support a wife who wanted to move out and live with her children. In Britain immigration has allowed polygamy to enter the country as well. In the U.S. numbers are harder to come by since most polygamists keep their practice secret but the number is growing as immigrants arrive who already have multiple wives.

Dr. McDermott says that her research encompasses more than 170 countries over the past decade and that she has seen the detrimental side effects of the practice. Human rights, for both men and women, suffer where polygamy is allowed. Women in polygamist cultures get married sooner, bear more children, have higher rates of HIV infection than men, sustain more domestic violence, succumb to more female genital mutilation and sex trafficking, and are more likely to die in childbirth. Their life expectancy is shorter than that of their monogamous sisters and their children, both boys and girls, are less likely to receive both primary and secondary education.

There are multiple reasons for these results but clearly polygamy is not good for women and women’s rights. When small numbers of men control larger numbers of women one of the most cherished of modern rights suffers. In this case religious freedom does not outweigh the social and moral consequences of allowing polygamy to spread.

Some fundamentalists argue that polygamy is biblically based since they see it in the Old Testament. This is not the place to debate the ethical norms of the Old Testament and how to interpret them but suffice it to say polygamy is a step backward for women and civilized societies. In this case the convergence of modern thought about women and the broader biblical model of justice and compassion argues against any relaxing of our laws against this practice.