<i>E. coli</i> (IMAGE) University of California - San Diego Caption <I>Escherichia coli</I> bacteria, like these in a false-color scanning electron micrograph by Thomas Deerinck at UC San Diego’s National Center for Microscopy and Imaging Research, cause a variety of often life-threatening conditions, particularly among the young. Varki and colleagues suggest a genetic change 100,000 or so years ago conferred improved protection from these microbes, and likely altered human evolutionary development. Credit Thomas Deerinck at UC San Diego’s National Center for Microscopy and Imaging Research Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.