Can we bring back a long-extinct animal?

Click here to read a slide-show essay about the quagga. In what would be an unprecedented feat, a South African amateur scientist says he is going to bring an animal back from extinction: the quagga. A large mammal that descended from the zebra, the quagga filled South Africa's plains for millennia. But it fell to gun-toting European colonists and was last seen alive in 1883.

How do you reverse extinction? And what is a quagga, anyway? Read this slide show to find out.