Final answer:
The fossil and archaeological records show that bipedal locomotion came before the creation of stone tools and the growth of the hominin brain. Advances in bipedalism by early hominids like the Australopithecines followed by Homo erectus enabled important evolutionary changes, such as the development of tools and potentially language.
Step-by-step explanation:
The fossil and archaeological records confirm that upright bipedal locomotion preceded stone tool manufacture and the expansion of the hominin brain. Early hominids like the australopithecines started walking on two feet, setting the stage for significant evolutionary developments. Among those, Homo erectus, which appeared around 2 million years ago (MYA), was highly adept at bipedalism, similar to modern humans in terms of efficiency. Evidence of early Homo species' refined bipedal abilities can also be observed in the fossil record, such as the Laetoli footprints discovered by Mary Leakey, dating back to 3.5 MYA. This adaptation to walking on two feet allowed for other profound changes, including the development of stone tools and possibly the precursors to human language. Homo erectus revolutionized tool technology, creating distinctive hand axes and requiring social learning and imitation to pass on these skills, potentially leading to the emergence of protolanguage. As the expensive tissue hypothesis suggests, the energy saved from lesser reliance on the gut for digestion in bipedal hominins could have been redirected to support larger brain growth. This larger brain capacity facilitated advancements in cognition and social interaction, such as complex tool use, which in turn may have played a role in the development of language.