| 1 | The elephant is the only mammal that can' t jump. | |
| 2 | Resignation and despair are well documented in other mammalian species. | |
| 3 | Our understanding of monogamy draws heavily on birds rather than mammals. | |
| 4 | The new tree bears on a longstanding dispute about the rise of birds and mammals. | |
| 5 | Birds and mammals invest in quality and not quantity, as opposed to fish and reptiles. |