Why did our ancestors ditch the shell and start growing babies inside their bodies instead? In this episode of Big Ideas, from the team behind Deep Look, Niba zooms out to explore one of evolution’s ...

Q. When we studied high school biology, our teacher said more than 99 percent of animals lay eggs and only a few give live birth. That percentage seems too high. Humans, dogs, cats and cows are ...

The oddball minority of animals that don’t lay eggs includes a tough little snail called a rough periwinkle. Unlike mammals giving birth to kittens and fawns and helpless little humans, this ...

Eggs helped animals conquer land—but most mammals stopped laying them. Why is that? Why do most animals lay eggs, while humans and most mammals give birth to live young? In this episode of Big Ideas ...