Dinosaur Image Gallery
Dinosaur Image Gallery

Carolina parakeets, now extinct. See our collection of dinosaur pictures.

John James Audubon/The Bridgeman Art Library/Getty Images

If you think of parrots as birds that live in lush, tropical jungles, you may be surprised to learn that the United States used to have its own native parrot. The Carolina parakeet lived in the American southeast until the early 20th century. These brightly colored, noisy birds were a nuisance. They ate fruits, vegetables and grains, and they traveled in large, noisy, crop-destroying flocks. This made them a favorite target of hunters, who wanted to protect the food supply and sell the birds' vivid feathers. If you want to see a Carolina parakeet today, you have to look for it in illustrations or stuffed museum displays -- it has died out completely due to hunting and habitat loss and was declared extinct in 1939.

Hundreds of years passed between the influx of European settlers on the coasts of North America and the extinction of the Carolina parakeet. But not all modern extinctions have been so slow in coming. Arctic explorers first made note of Stellar's sea cow, which looked like an extra large, wrinkly manatee, in 1741. By 1768, less than 30 years later, excessive hunting led to the sea cow's extinction.

These are just two of the life forms that have died out since mankind started keeping records. But today's research suggests that these extinctions may be part of a bigger trend -- a human-caused mass extinction that could rival prehistoric events that destroyed most life on Earth. The most famous of these was the mass extinction that killed the dinosaurs, although other events were far more devastating.

Whether they're big or small, extinctions change the world. And while extinctions themselves are all about change, the study of extinction is all about uncertainty. Anything that lives can become extinct, but how do scientists know when it happens? How is it possible to figure out how quickly species are disappearing when no one really knows how many species live on Earth in the first place? This article will delve into what happens when species disappear, from dinosaurs to dodos, and explore the question of how new life can arise from widespread extinction.