More than half of Americans now live within 50 miles of ocean, but should they? John Gillis (Rutgers University), in his new book The Human Shore: Seacoasts in History, argues that an inadequate understanding of the natural and human history of our shores has left communities unprepared for coastal dwelling.  John will speak at the Harvard Museum of Natural History, 26 Oxford Street in Cambridge, on Sunday, June 23 beginning at 3:30 pm.  For more information visit www.hmnh.harvard.edu/lectures_and_special_events/index.php.  Regular Museum admission rates apply.