The origin and early evolution of quadrupeds is a long-standing mystery in zoology and evolutionary biology. In the past two decades, however, studies on metazoan higher-level phylogeny and evolution made a considerable headway thanks to the rapid development of molecular biology and, in particular, the application of the molecular systematics. On May 18, 2011, Dr. Zhang Changsheng, an associate researcher of BMNH, gave a public lecture on molecular evolution.