American scientist Ben Novak has spent the past six years working on a process referred to as de-extinction—with the goal of bringing back the passenger pigeon species that died off in 1914. In Melbourne, Australia Novak has used gene-editing to weave the Cas9 gene into the reproductive organs of common pigeons. Cas9 enables the use of CRISPR, a tool that acts as molecular scissors and enables a cut-paste of DNA. Soon, perhaps, Novak will see to the passenger pigeon’s return. This could lead to the reemergence of the dodo or even the woolly mammoth—and that will bring up greater questions over what it means to bring an extinct species back, whether we should, and what happens if re-extinction occurs. Read more about the process at the Wall Street Journal.