The Evolving Definition of a Gene
928 BioScience • December 2009 / Vol. 59 No. 11 www.biosciencemag.org There was a time when a biologist could discover a new species by strolling into a field and saying, “What, ho! I’ve never seen one of those before!” Of course, by now biologists have seen it all—or at least all of the things that are easy to see. So a scientist who spies something seemingly new first needs to consider whether that creature belongs to a previously identified species.