Darwin's original thesis, and the viewpoint supported by evolutionary gradualists, is that species change continuously but slowly and in small increments.
达尔文最初的论点以及进化渐进主义者所支持的观点是，物种的变化是持续的，但非常缓慢，增量也很小。
2
Gradualists believe that the cause of the demise of the dinosaurs was over competition by mammals and gradual climatic changes caused by plate tectonics.