anthemaniac writes "Professor Esmail Zanjani and colleagues at the University of Nevada-Reno have created sheep that are 15 percent human at the cellular level. Half the organs in the sheep are human. The idea, of course, is to harvest those organs to transplant into human patients. From the article: 'He has already created a sheep liver which has a large proportion of human cells and eventually hopes to precisely match a sheep to a transplant patient, using their own stem cells to create their own flock of sheep.' One scientists worries, however, that the work could lead to new viruses that cross from animals to humans."