Slime is all around and inside you – new research on its origins offers insight into genetic evolution

Slime is everywhere. It shapes the consistency of your bodily fluids, from the saliva in your mouth to the goo that covers your organs. It protects you against pathogens, including coronavirus, while creating a home in your mouth for billions of friendly bacteria. It helps slugs have Spiderman sex hanging from walls, hagfish turn water into rapidly expanding goo, lampreys filter their food and swiftlets build nests.

But while slime is essential for all forms of complex life, its evolutionary origins have remained murky.

I am an evolutionary geneticist who studies how humans and their genomes evolve. Along with my colleagues, including my long-time collaborator Stefan Ruhl and my student Petar Pajic, we tackled this evolutionary puzzle in our recently published paper. We began by looking into how salivary slime is made in different species. What we found was that slime opens a window into the role that repetitive DNA plays in the mysteries of evolution.