The 1:1 ratio results from the way the X and Y chromosomes are doled out in sperm and eggs. We know that boys and girls are produced in much the same frequency. But how – and why – is this 1:1 ...

To keep up to date with the latest Number 1s each week, sign up to our newsletter. Unsubscribe at any time.

The browser you are using is no longer supported on this site. It is highly recommended that you use the latest versions of a supported browser in order to receive an optimal viewing experience.