translation.en: like lampreys, which are very primitive fish, and then gradually go toward more complex locomotion, like in salamanders, but also in cats and in humans, in mammals.
translation.zh: 这种原始的鱼类 然后慢慢过渡到运动更复杂的动物 例如蝾螈 然后还有猫、人类 等哺乳动物 这样一来