Savino di Lernia, an author of the study and the Director of the Archaeological Mission of the Sapienza University of Rome, has been working in Libya since 1990. He says that around 12,000 years ago, shifts in monsoon patterns brought rain to the region. With increased rain grew waterways that connected to Lake Chad in the south and the Nile River in the north, possibly opening up a passage for these fish to reach the central Sahara in such quantities.