Final answer:
Homo erectus were the first hominins to walk upright and use tools.
Step-by-step explanation:
Scientists believe that hominins in the Homo erectus (Upright Man) group were the first to walk upright and use tools. Homo erectus emerged around two million years ago and lived exclusively on the ground in an upright position, which allowed their hands to be free for tool use. They had a larger brain and were similar in size to modern humans. Homo erectus is also believed to be the first hominin species to migrate out of Africa.