This week we're learning about genetics research that could help preserve existing species, and might let us bring back others that have gone extinct. We'll talk to Beth Shapiro, professor of ecology and evolutionary biology at the University of California, Santa Cruz about her book "How to Clone a Mammoth: The Science of De-Extinction." And we'll speak to biologist Richard Frankham about the use of "genetic rescue" to keep isolated animal populations from becoming dangerously inbred.