It's a little bit light on detail, and the article it's referring to (in Science) is pay-walled, but here's the abstract: http://www.sciencemag.org/cgi/content

It's a little bit light on detail, and the article it's referring to (in Science) is pay-walled, but here's the abstract: http://www.sciencemag.org/cgi/content/abstract/327/5964/439 http://www.sciencemag.org/cgi/content/abstract/327/5964/439