Origins.  [electronic resource] 

 -  Scientific American  Aug 2010 
 - 46-53 p.  digital 
<br/><br/> Publication Type: Journal Article 
<br/><br/><label>ISSN: </label>0036-8733 
<br/><br/><label>Standard No.: </label>10.1038/scientificamerican0810-46  doi