Sloths look slow in a way that almost doesn’t feel real, but their sluggish movement isn’t a flaw or a weakness. Every part of their body is built around saving energy, avoiding danger, and surviving ...

Millions of years ago, some ancestors of today's sloths were the size of elephants. Ground sloths, as they are called, used to roam the earth and graze from the treetops. They are believed to have ...