much better bug-munchers

entirely new ecosystem had been invented,

There’s another clue that therapsids were raising their metabolisms and better controlling their body heat. Hair.

The Pennsylvanian trees—and the supersize dragonflies that buzzed around their branches and millipedes that scurried around their trunks—were able to grow so large because there was much more oxygen in the air then, some 70 percent more than today.

triggered a domino chain of changes to mammalian feeding, intelligence, and reproduction.

mammals that find themselves washed up on islands are known to change aspects of their biology and behavior to adapt to the constraints of their new home. One of the most common

two key features of mammals. The olfactory bulbs—which orchestrate the sense of smell—are massive. And the top of the cerebrum boasts a new structure: a six-layered mass of nervous tissue called the neocortex,

Along the torso, the vertebrae abruptly lost their ribs, where the thoracic region transitioned to the lumbar region. This is a telltale sign of a diaphragm—the powerful muscle that draws air into the lungs.

Volcanoes did it—so-called