"Sex is both complex and dangerous, so why do we and almost all other species do it?" asks John Logsdon, University of Iowa associate professor of biology in the College of Liberal Arts and Sciences. Evolutionary biologists really aren’t sure, but Logsdon plans to tackle the issue in a UI Explorers Lecture sponsored by the Museum of Natural History on Thursday, Oct. 21. The 7 p.m. lecture will take place in the Museum’s Biosphere Discovery Hub in Macbride Hall and is free and open to the public.