When we think about cooperative behaviour, most of us would think of animals like ants, meerkats, lions or, indeed, humans. But don’t rule out yeast. The small, single-celled fungus has provided us with much of our knowledge of genetics and molecular biology and now, it’s shedding light on the evolution of cooperation too.

The budding yeast, Saccharomyces cerevisiae, is one of the most widely studied of laboratory microbes, but scientists mostly know it as a solitary species. Brewers, on the other hand, use S.cerevisiae to make beer and are all too aware of its social side. Their strains have a tendency to form large clumps, or “flocs”, which makes them easier to remove from beer once fermentation is complete. This