 This is Think. I'm Chris Boyd. Today we're talking about the practical and ethical considerations of pet cloning. My guest, Alexandra Horowitz, is Senior Research Fellow and Head of the Dog Cognition Lab at Barnard College at Columbia University. Her article for The New Yorker is titled, Would You Clone Your Dog? Just to step back here for a minute, Alexandra, we've talked a bit about Dolly the sheep. How long have scientists had the ability to successfully clone mammals?