To estimate the timing of the origin of various major animal groups, Gregory Wray of Duke University and his colleagues used a molecular clock rate based on vertebrates (animals that have a backbone).

• 为了估计各个主要动物类群的起源时间，美国杜克大学的瑞伊（GregoryWray）与同事使用了以脊椎动物为基础的分子时钟。