The evolution from fin to limb took millions of years. 从鳍到肢的进化用了数百万年
Key was the evolution of a new compound, 其关键是一种新化合物的进化
...to the evolution of hard-shelled eggs 再到硬壳卵的进化
With them, one of the links in a long chain of evolution snaps. 进化长链中的一环随之断裂
Ross: Watch something like this and you realize why evolution is just a theory. 看看这个,你就知道为什么进化仅仅是理论上的事情。