为什么父亲想要男孩而母亲喜欢女孩？

That tired truism about wanting only a healthy baby and not caring about gender? Puh-leeze. Women want daughters, and men crave sons, finds research in the journal Open Anthropology.

The results surprised even the researchers, from Queen’s University in Ontario, Canada, who’d surveyed more than 2,000 students, staff and faculty at the college about gender preference in offspring. They’d assumed that respondents would show little or no preference, but they found that — no matter how they worded the question — there was a “significant offspring gender preference” along gender lines.

Respondents answered the following questions:

1. What gender would you prefer your firstborn child to be (or did you hope for if you already have a child)?

2. If you were to have (or do have) more than one child, would you prefer the majority to be male or female?

3. If you were to have only one child, what gender would you prefer it to be?

“Today, offspring gender preference conflicts with the ongoing mission in many nations, especially in Western Europe and North America, to pursue social and political agendas aimed at eliminating all discrimination on the basis of gender,” write the authors.

And yet, it persists. What gives?

Men’s preference for sons is pretty easy to explain in terms of evolution. Males have a greater chance of perpetuating the family genes by fathering far more children than a woman could ever bear. Women’s preference for daughters is more nuanced. Maybe it’s a maternal desire to have a shared experience of pregnancy, or maybe women are subscribing to visions of perceived mom-daughter emotional bonds. Call it a “legacy drive,” say the authors, and consider that modern women are so infused with pride over their social and financial empowerment that they want to share the good life with their girls. “There is currently a tendency in North American society to place a high degree of emphasis on realizing one’s own ‘success’ through the success of one’s children,” write the authors. “The present data suggest that this opportunity for legacy is envisioned for males generally through sons, but for females generally through daughters.”

The study didn’t look at thornier questions of whether would-be parents are so committed to the idea of having a child of the same sex that they would practice gender selection to achieve their dreams. But an editorial published in the current edition of the Canadian Medical Association Journal makes the case that parents shouldn’t learn their baby-to-be’s sex until after 30 weeks of pregnancy when abortions are no longer permitted. Female feticide — aborting girls — isn’t unusual in countries including India and China, but it’s apparently also happening in some ethnic groups in Canada and the US.

“This evil devalues women,” writes Dr. Rajendra Kale, the journal’s interim editor-in-chief. “How can it be curbed? The solution is to postpone the disclosure of medically irrelevant information to women until after about 30 weeks of pregnancy.”

That probably wouldn’t go over well stateside, where pregnant women have become accustomed to learning their baby’s sex courtesy of an ultrasound wand before 20 weeks.

“A pregnant woman being told the sex of the fetus at ultrasonography at a time when an unquestioned abortion is possible is the starting point of female feticide from a health care perspective,” writes Dr. Kale. Although a woman has a right to information about herself that relates to her health and medical care, “the sex of the fetus is medically irrelevant information (except when managing rare sex-linked illnesses) and does not affect care.”