Obituary: Dan S Tawfik (1955-2021).

Dan (Danny) Tawfik, a leader in biochemistry and protein evolution, sadly died due to a fatal climbing accident on May 4th, 2021. Apart from science, rock climbing was Danny's passion and a source of pride as only a handful of researchers are active climbers. Danny made unique and long-lasting contributions to our understanding of molecular evolution. He was also incredibly generous with his time and insights, and many researchers around the world are indebted to him, not least the two authors of this obituary.