Japanese scientists have discovered a way to slow down sperm that carry the X chromosome. The sperm bearing X chromosome gives rise to daughters and the sperm with the Y chromosome gives rise to sons. A kind of chemical has been found to make the X-bearing sperm slower at swimming without affecting their fertilization ability. 

In principle, this allows for users to separate sperm according to the sex of the offspring that they want to produce. The research was focused on livestock and the technique was found to be successful with cattle and pigs. Sex selection is important in lifestock because it leads to more humane farming; bulls are of limited use to dairy farmers, while beef producers prefer males.

It is possible that there would be a commercial method for sorting human sperm within the next ten years. While there are already existing methods for sex determination, this chemical method would make sperm sorting certain and therefore sex selection more widely available.

Read the full article on New Scientist: Sperm sorting method could prevent girls being born, scientists warn


There is a concern that such technology would lead to the further skewing of sex ratios, particularly in countries where there is already a preference for male offsprings. When societies value sons over daughters and family sizes become smaller, the research shows an increase in sex-selective abortions where female fetuses are aborted in families which are trying for sons.

Even if the preference for males does not lead to female infanticide, there may also be a differential treatment of the sexes. Females who are born may receive fewer resources compared to males or neglected. On a larger scale, the imbalance of the sex ratio threatens social instability. With the high surplus of males, many will remain single and be unhappy to find partners or eventually to have families. 

Currently, selecting for sex except for medical purposes is banned in many countries. However, it is permissible in the US where some use it to balance their families. Nevertheless, sex selection is inherently problematic because it tends to reinforce sexist stereotypes by devaluing women.

Questions for further personal evaluation: 

  1. Are family balancing reasons sufficient cause to engage in sex selection practices? 
  2. Are the ethical concerns different based on the type of sex selection? Does it matter that the sex selection occurs at the sperm stage or the embryo/ fetus stage?

Useful vocabulary: 

  • ‘infanticide’: practice of killing unwanted children soon after birth
  • differential’: depending on a difference; varying according to circumstances or other factors