An interesting essay on the arrival of a nucleus in cells, a major advance over bacteria, for instance, with no nucleus. A nucleus is needed for sex to appear: - http://www.sciencemag.org/cgi/content/summary/325/5941/666?sa_campaign=Email/toc/7-Augu... - Please note the usual problem: no transitional forms. - Read 'false alarm', 'zombies' and 'out of order' to see tricks of nature and brain development in evolution: - http://sciencenow.sciencemag.org/science-shots/