【英语时差8,16】食肉鲸和食素鲸

（单词翻译）

 Everyone is familiar with the riddle¹: Which came first, the chicken or the egg? This sometimes leads to discussions about bird evolution. But most people don’t realize this type of question is common in paleontology. For example: Which came first, the meat-eating whale ancestor or the plant-eating one? Answering that question has not been easy. Early fossil finds suggested whales might be related to the mesonychids, an extinct group of wolf sized, hoof² toed carnivores. These mammals had triangular³ teeth similar to whales. But when genetic⁴ analysis began, that idea was put to the test. You see, scientists comparing DNA⁵ of whales to other mammals found that whales were most closely related to plant eating ungulates. This group includes sheep, antelopes⁶ and pigs. As a matter of fact, the closest living relative to whales is the hippopotamus⁷. So, how is it that modern whales are meat eaters?