Utahraptor, up to 7 feet long, with early feathers
(palaeocritti.com)

Not dinosaurs exactly, but their descendants for sure. Look outside for the creatures that lay eggs and walk semi-upright on two legs, with a stiffened tail. Imagine that that robin is many times larger, without feathers but with scales, with a large jaw instead of a beak, with long forearms instead of full wings, and you have a creature out of Jurassic Park. A topic of speculation since Darwin’s time, the descent of birds from dinosaurs has been confirmed by recent fossil discoveries. Natural selection works in wondrous ways.

How did the dinosaurs of 200 million years ago get feathers? The feathers first appeared because they helped a dinosaur stay warm. But they had a second, accidental benefit. When a dinosaur was running, its feathers provided balance and lift. Eventually, according to the most widely accepted theory, lift became lift-off. (The familiar Pterodactyl flew on wings of skin and membrane; it was neither bird nor, officially, a dinosaur.)

From dinosaur to bird. Archaeopteryx lived 150 million years ago and was about the size of a crow. It had both a dinosaur’s sharp teeth and a bird’s feathers. This 1880 photo shows feathers that were later removed. (wikipedia)

And where were our own ancestors, the mammals, while all this was going on? Early mammals were small and stayed  out of the way of the meat-eating reptiles. They bore young that had grown inside the mother instead of inside eggs, reptilian style.

Juramala, a mouse-size mammal living 160 millions year ago. Like humans, it had a neo-cortex and nourished its young until birth through an umbilical chord. (physorg.com)

And they carried a brain more complex than the old “lizard brain.” The bigger brain, with its neo-cortex, improved their sensory perception and movement. We also use it to think and imagine.

Feathers and wings, and the new brain—all of them selected for survival and adapted for soaring.