Superslow sloths may have once evolved superfast
![Two-toed sloth](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2014/09/sloth_free_0.jpg?fit=860%2C460&ssl=1)
Two-toed sloths like this one weigh about 6 kilograms. Their extinct cousins were once thousands of kilograms, suggesting that these slow creatures once evolved quickly.
Jsfouche/Wikimedia Commons (CC BY-SA 3.0)