Kallikrein related peptidase 8 (KLK8; also called neuropsin) is a serine protease that plays distinct roles in the skin and hippocampus. In the skin, KLK8 influences keratinocyte proliferation and desquamation, and activates antimicrobial peptides in sweat. In the hippocampus, KLK8 affects memory acquisition. Here, we examined the evolution of KLK8 in mammals and discovered that, out of 70 plac...