In a cauldron of boiling, acidic water, kneeling at the foot of a Russian volcano, one species of microbe is on the cusp of becoming two.

Now, Rachel Whitaker from the University of Illinois has found that the species has pretty much split into two separate lineages. Both share the same water, and they can trade genes with one another, but they have started to part ways and are becoming increasingly distant. In this hot, hostile and acidic world, the origin of the species is playing out before our eyes.

Whitaker collected 12 strains of S.islandicus from one of the Mutnovsky springs, sequenced their complete genomes and charted their evolutionary relationships. They were remarkably similar. At most, any two strains differed in