Through observations of chimpanzees and bonobos, Hiroyuki Takemoto, a researcher at the Primate Research Institute at Kyoto University, discovered that changes in forest temperature and their seasonal changes are the main factors that increase the amount of time spent on the ground.
The reason why human ancestors began to live on the ground has been attributed to the decrease in forest area in Africa due to the aridity that occurred in the late Miocene after about 900 million years ago.However, all early human fossils have been found in environments close to forests.This means that human terrestrial life had already begun when forests were the main habitat.However, it remained unclear why it was necessary to descend to the ground for forest life.
In this study, we observed African fat-tailed gimpanzees living in forests with large seasonal changes and bonobos living in Central Africa with little seasonal changes.Both species are above the ground for more than half a day on hot days, but spend most of their time on trees and never land on cold days.It was thought that the energy of thermoregulation was saved by spending time in the upper part of the warm forest (canopy) in the cold rainy season and on the cool ground in the hot dry season.In the forest where bonobos live, the seasonal difference in temperature is small, so if we take the average for each season, the ground usage time remains small and does not change.In other words, it was found that seasonal changes in forest temperature are the main factors that increase the time spent on the ground.
This report suggests that human ancestors who lived on warm, moist rainforest trees all year round were encouraged to live on the ground in the forest by the emergence and prolongation of the late Miocene dry season. Be done.After the retreat, the ability to adapt to the open environment dotted with trees seems to have been contributed by the experience of seasonal ground life in the forest.This achievement is said to have great significance in considering the evolution of early human beings, such as erect bipedalism.
Paper information:[Scientific Reports] Acquisition of terrestrial life by human ancestors influenced by forest microclimate
