Every few years, we get a recycling of old explanations for women’s underrepresentation in traditionally male fields, and these inevitably circle around babies and biology. Either women “just want to have kids,” so cannot hold down serious jobs, or women are wired to be less capable in certain fields. Most recently, these arguments were recycled as an explanation for women’s low representation in science and engineering fields by Stephen Ceci and Wendy Williams. They argued that there is no longer evidence of sex discrimination, so we should switch our policy focus to “make institutions responsive to different biological realities of the sexes.” This is the biology-based version of the women “just want to have kids” argument.

In a response published this week, I note that the biology argument is static, so it might explain persistent sex segregation. It cannot explain changing patterns of segregation, and that is what occurred with a three-decade intensification of sex segregation within science and engineering fields. Here’s what happened: according to figures produced by the National Science Foundation, between 1977 and 2009, out of all new science and engineering doctorates in the U.S., women became more concentrated in the life sciences (rising from 65% to 74% of all women’s science and engineering doctorates), while men became more concentrated in other science and engineering fields (their percentage in life sciences fell from 38% to 37%).

Women’s supposed love of children cannot explain this shift, but language and laws can. It turns out that the decrease in men’s representation in life sciences is due to an influx of foreign national men. Among men who are American citizens, the percentage of life science degrees rose, including for White non-Hispanics (40% to 49%), Black non-Hispanics (41% to 57%), and Hispanics (35% to 50%). In other words, the gender of American citizens had nothing to do with the increase in sex segregation.

So why are foreign national men flocking to science and engineering programs outside of the life sciences? Language has something to do with this, with life sciences doctorates requiring relatively greater English language abilities.

Of course, this begs the question of why foreign national women are not entering non-life science fields in large numbers . And to answer that question requires a bit of history: then-President Nixon signed Title IX into law in 1972, opening the doors of colleges and universities across the U.S. to women. We have made great progress in terms of gender equality since then: women received a whopping 54% of all science and engineering doctorates earned by U.S. citizens in 2009. But other nations do not have Title IX and, as a result, women earned only 32% of new science and engineering doctorates among foreign nationals.

I get that care for kids often conflicts with job demands. But those conflicts, and the low numbers of foreign national women in science and engineering, have more to do with culture and laws than biology.