In 1980, anthropologists Tom Hatley and John Kappelman suggested that early hominins (convergently with bears and pigs) adapted to eating abrasive and calorie-rich underground storage organs (USOs), such as roots and tubers. Since then, hominin exploitation of USOs has gained more support. In 2005, biological anthropologists Greg Laden and Richard Wrangham proposed that "Paranthropus" relied on USOs as a fallback or possibly primary food source, and noted that there may be a correlation between high USO abundance and hominin occupation. In this model, "P. boisei" may have been a generalist feeder with a predilection for USOs, and may have gone extinct due to an aridity trend and a resultant decline in USOs in tandem with increasing competition with baboons and "Homo". Like modern forest chimps and baboons, australopithecines likely foraged for food in the cooler morning and evening instead of in the heat of the day.