In this episode, Patrick is joined by Alex Cagan, a Postdoctoral Fellow in the Cancer, Ageing and Somatic Mutation programme at the Wellcome Sanger Institute, specialising in evolutionary processes in somatic tissue. Tune in as Alex walks us through a fascinating new study, years in the making, looking at somatic mutation rates across 16 mammalian species, spanning 30-fold in lifespan and around 40,000-fold in body mass. This work sheds light on fundamental questions in cancer and ageing across the tree of life. 0:00 Intro 6:00 Collaborating with the London Zoo, and the challenges of sourcing tissue from long-living animals 9:06 Why are naked mole rats so important to the cancer and ageing community? 11:32 The scale and breadth of species sampled in the study 14:53 Is there a ceiling to how many mutations an organism can tolerate? 17:53 Why are intestinal crypts so effective for sequencing somatic mutations? 20:44 Key learnings from driving a 5-year study into somatic evolution 22:46 Are there really any “immortal” species, and what are they? 25:19 Why are cancer rates lower in larger species, and is this related to lower mutation rates, DNA error correction or both? 27:24 Investigating transmissible cancers in Chernobyl 29:40 Is cancer everywhere in the tree of life? 31:23 Alex talks about applying his talent for illustration to science 38:56 The Sanger Tree of Life program, the Darwin Tree of Life project, and the bright future ahead for research on somatic mutations 40:14 Outro Find out more about the study: https://www.nature.com/articles/s41586-022-04618-z