What led scientists to believe that Homo erectus was the nearest ancestor to humans?

Scientists believe Homo erectus is a likely ancestor of humans because of its physical similarities to modern humans, such as upright posture and increased brain size compared to earlier hominins. Additionally, Homo erectus is thought to have used more advanced tools and had a more complex social structure than earlier species, suggesting a closer relationship to modern humans. Fossil evidence, such as those found in Africa and Asia, also support the idea that Homo erectus is a key transitional species in human evolution.