London, United Kingdom. New findings argue for the persistence of sex-linked chromosomes, such as the male Y chromosome, refuting theories that the Y is doomed to extinction.

The results confirm that although these chromosomes have shrunk over millions of years, and have lost many of their original genes, those that remain are extremely important in predicting fertility and are, therefore, unlikely to become extinct.

Before I built a wall I'd ask to know
What I was walling in or walling out,

—  Robert Frost, Mending Wall

Waltham, MA, USA. In rural New England, as in much of the rest of the world, people mark their territory, like some race of architecturally-adept spaniels, by building a wall around its borders.