Cloning Image Gallery
Cloning Image Gallery

A 5th-century bronze depicts the wounded Chimera of Lycia. Today's scientists are creating their own version of the chimera. See more cloning pictures.

Bridgeman Art Library/Getty Images

­Thousands of years ago, the Greek poet ­Homer wrote about a specific monster that seems to haunt humanity to this day. Khimaira had the chest of a lion, the tail of a snake, the midsection of a goat and heads of all three animals. The term chimera -- a single creature made up of more than one species of a­nimal -- comes from that mythological beast. Chimeras, however, are not mythological.

When the Britis­h government's organization for science oversight approved a request to create human-pig hybrids in December 2007, there was uproar in the country. The extent of the debate, both bioethical and scientific, seemed to reflect the approval of a brand-new science. Chimeras, however, aren't new. They're just not that well publicized, because previous research in combining species has been carried out primarily in countries that don't require public­ disclosure of research-science requests, like the United St­ates and China.

Researchers at Shanghai Second University have combined humans and rabbits [source: Telegraph]. Mayo Clinic scientists in Minnesota have already created pigs that have human blood, and a Stanford researcher developed mice whose brains are 1 percent human, with the ultimate goal of creating mice with entirely human brains [source: National Geographic]. It's not actually new in Britain, either: Human-cow embryos have been growing in London for quite some time.

You may even know a chimera, yourself. Technically, transplant patients who've received heart valves from a pig are chimeras. Along those lines, some of the chimera research to date has focused on how to create animal organs that are partly human so the human body has a better chance of accepting that kind of transplant. Some of it focuses on creating an egg to aid in human fertility research, since human eggs are hard to come by and are very expensive. Other research, though, including the new research at the University of Warwick in the United Kingdom, has different, albeit related, goals.

In this article, we'll find out what the human-pig hybrid is all about, how researchers will create it, what they hope to achieve and why some people are staunchly against it. We'll also answer the question that's probably sitting in the back of your mind right now: Will we soon be seeing real pictures of a human being with hooves?

Let's find out. First, how do you create a chimera?