In this Aug. 15, 2017 photo, paleontologist Ashley Leger shows the skull of a young Columbian mammoth found at the construction site of the Metro Purple Line extension in Los Angeles. The Los Angeles subway system is expanding and so too are the number of prehistoric fossils being recovered as crews dig beneath the city. Since work on one extension began in 2014, workers have routinely turned up fossilized remains of rabbits, camels, bison and other creatures that roamed the region during the last Ice Age. (AP Photo/Jae C. Hong)