When Rutgers geologist Daniel Deocampo first came across what looked like a rough dirt road (center) that seemed to lead nowhere in a remote part of Tanzania, he wasn’t quite sure what to make of it. Eventually he figured out that paths like this are the remains of hippo trails to dried-up wallowing pools. Hippos wallow in freshwater pools during the day to escape the sun (right); at night they plow through the mud to grasslands to eat, trampling out hippo highways in the process. Deocampo recently came upon something very similar near Olduvai Gorge, where some of the oldest hominid fossils have been found. He spied a U- shaped trench (outlined below left) four and a half feet wide and four and a half feet deep embedded in 1.75-million-year-old sediments that had been excavated in 1995. Deocampo identified the trench as a fossil hippo trail. What excites me, he says, is seeing how even though these fossils record what happened millions of years ago, we can still see some of those same processes going on today.