Tiny structural errors in proteins may have been responsible for changes that sparked complex life, researchers say.
A comparison of proteins across 36 modern species suggests that protein flaws called "dehydrons" may have made proteins less stable in water.
This would have made them more adhesive and more likely to end up working together, building up complex function.
The Nature study adds weight to the idea that natural selection is not the only means by which complexity rises.
Natural selection is a theory with no equal in terms of its power to explain how organisms and populations survive through the ages; Random Mutations that are helpful to an organism are maintained while Harmful ones are bred out.
But the study provides evidence that the "adaptive" nature of the changes it wreaks may not be the only way that complexity grew.