THE economic turmoil that followed the fall of the Berlin Wall in 1990 may have forced down the number of boys born in what was then East Germany.
Stress during early pregnancy is known to reduce the proportion of males born in many species. The theory is that natural selection favours female births when times are hard because, on average, they have a better chance of mating successfully than males do.
Now Ralph Catalano at the University of California, Berkeley, has shown that this may happen in humans too. Birth records show that in 1991, immediately after Germany was reunified,…
