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.
