Two become one: two raven lineages merge in 'speciation reversal'

After up to two million years of separate evolution, two types of common raven have been 'caught in the act' of consolidation, say scientists

Speciation, where one species diverges into two, is a well-known concept in the theory of evolution. But a new study based on almost 20 years of research has revealed that "speciation reversal", the merging of two previously distinct lineages, may also play an important role.

Scientists have discovered that two lineages of common raven that spent between one and two million years evolving separately appear to be in the process of such a consolidation. The findings raise intriguing questions about how science should define species - and whether the boundaries are as clearcut as once thought.