How complex innovations can emerge seemingly out of nowhere is a central question of evolutionary biology. Researchers at the Leibniz Institute for the Analysis of Biodiversity Change (LIB) discovered new evidence that inflammatory immune responses can lay the foundation for the evolution of novel tissues. This process led to the emergence of a unique tissue called “plug”, which allows ricefish mothers to carry their offspring until hatching. Such an “innovative inflammation” not only revolutionized ricefish reproduction, but also played a key role in human evolution.