Nineteen previously unidentified pieces of non-human DNA — left by retroviruses that first infected human ancestors hundreds of thousands of years ago — have been found by scientists in a study of 2,500 human genomes. According to the team, one stretch of newfound DNA, found in about 50 of the 2,500 genomes studied, contains an intact ancient virus – only the second such virus described. This electron micrograph shows particles of...
