MELBOURNE, FLORIDA—Some scholars have argued that today’s Amazonian rainforests are the result of ancient managed landscapes, but a new study suggests that people who lived in Amazonian forests prior to the arrival of Europeans had dense settlements in areas near rivers and little impact at all on other areas. Dolores Piperno of the American Museum of Natural History and Mark Bush of the Florida Institute of Technology examined plant fossils, estimates of mammal density, and information from remote sensing and human population modeling, and found that Amazonian forests in remote regions are slow-growing, fragile ecosystems that may be very vulnerable to logging, mining, and other disruptive enterprises. “Nobody doubts the importance of human actions along the major waterways. But whether humans had a greater impact on the ecosystem than any other large mammal has yet to be established in much of western Amazonia,” Bush explained in a press release. To read about work in Mesoamerican rainforests, go to "Lasers in the Jungle."