"We show in this paper that even these abrupt changes are easily explained as cases of what is known as 'directional selection' -- when natural selection strongly pulls a trait in one direction.

Stroud expected to observe stabilizing selection at work preserving moderate traits. Instead he saw clearer evidence of directional selection: some lizards with unique traits, such as stickier ...

Known in evolutionary biology as “directional selection,” this process is like the sharpening of a knife—while the weapon gets more deadly, it loses a bit of itself in the process. The new study ...

“We predict that this weak directional selection has led to a 10 to 20 per cent increase in the rate of fetopelvic disproportion since the regular use of Caesarean sections,” said lead author ...