Dolphins are commonly kept in captivity and are even sometimes trained to perform tricks and tasks, other cetaceans aren't as often kept in captivity (with usually unsuccessful attempts).
Cetaceans have been relentlessly hunted by commercial industries for their products, although this is now forbidden by international law.
Some species are well adapted for diving to great depths.
Although cetaceans are widespread, most species prefer the colder waters of the Northern and Southern Hemispheres.
The two parvorders, baleen whales (Mysticeti) and toothed whales (Odontoceti), are thought to have diverged around thirty-four million years ago.