Sponges are among earth’s most ancient animals, but exactly when they evolved has long puzzled scientists. Genetic information from living sponges, as well as chemical signals from ancient rocks, suggest sponges evolved at least 650 million years ago. This evidence has proved highly controversial as it predates the fossil record of sponges by a minimum of 100 million years. Now an international team of scientists led by Dr Eleonora Rossi, from the University of Bristol’s School of Biological Sciences, have solved this conflict by examining the evolution of sponge skeletons. The research is published in Science Advances.