www.sciencemag.org (this information is current as of January 5, 2009 ): The following resources related to this article are available online at http://www.sciencemag.org/cgi/content/full/322/5907/1494 version of this article at: including high-resolution figures, can be found in the online Updated information and services, found at: can be related to this article A list of selected additional ...