www.sciencemag.org (this information is current as of February 21, 2008 ): The following resources related to this article are available online at http://www.sciencemag.org/cgi/content/full/299/5613/1728 version of this article at: including high-resolution figures, can be found in the online Updated information and services, http://www.sciencemag.org/cgi/content/full/299/5613/1728/DC1 can be f...