Traditional theories suggest that human ancestors were forced to leave the arboreal environment and chose to walk upright on the ground due to climate change and reduced trees. A new study suggests that early human upright walking originated from the rugged mountains of eastern and southern Africa today. The terrain was formed by a volcanic eruption and tectonic plate movement during the Pliocene period. Human ancestors were attracted by rocky terrain and canyons, which provided good shelter habitats and opportunities to trap prey; this environment required early humans to be upright The ability to walk and climb, so human ancestors eventually evolved into bipedal upright walking. Based on the above, which of the following can be introduced is:. ['The destruction of the arboreal environment has forced people into the mountain canyons.', 'Human ancestors chose to walk upright to better adapt to the terrain environment.', 'Changes in geological conditions changed the way early ancestors of humans walked.', 'Canyon area provides richer food resources.']