Final answer:
Homo erectus, or 'upright man', was a significant ancestor of modern humans who lived around 2 million years ago. Known for its upright posture, advanced tool use, and increased brain size, it spread from Africa to Eurasia and marked a substantial step in human evolution.
Step-by-step explanation:
Homo erectus (Upright Man): Homo erectus, which means 'upright man' in Latin, emerged around 2 million years ago in East Africa. This early human ancestor is known for being the first to have an upright bipedal gait, allowing it to live entirely on the ground. The anatomical changes necessary for their upright posture also led to changes in the body structure, such as the positioning of digestive organs and adaptations in diet that included a variety of foods like nuts, fruits, tubers, honey, and meat. Their hands were freed, enabling them to use tools more effectively which facilitated further evolutionary developments. With a brain capacity ranging from 1,000 to 1,200 cubic centimeters, Homo erectus exhibited more advanced cognitive abilities compared to its predecessors. The species also had notable physical features, including an uninterrupted brow bone and a nose that pointed downward, much like modern humans. Homo erectus not only survived in a variety of environments but spread from Africa to parts of Europe and Asia, with their remains found in regions as far-reaching as Java, Indonesia. The species was longer-lived in the human evolutionary timeline, possibly surviving until around 300,000 to 25,000 years ago in eastern Asia. As a descendant of Australopithecus and possibly giving rise to various forms of archaic humans, including Homo heidelbergensis and Homo neanderthalensis, Homo erectus had significant contributions to the human lineage. Through their development of more advanced stone tool-making techniques and potential use of fire, they marked an important evolutionary step towards the more modern Homo sapiens.