Final answer:
The earliest trait during human evolution is believed to be obligate terrestrial bipedalism, which provided advantages such as freeing hands to carry tools and resources and improving energy efficiency. Reduced nonhoning canines, large brains, and stone tools developed later in human evolution.
Step-by-step explanation:
The evolution of human traits such as obligate terrestrial bipedalism, reduced nonhoning canines, large brains, and stone tools is a complex and intertwined process that occurred over millions of years. However, based on current scientific understanding and the available evidence, the earliest of these traits during human evolution is believed to be obligate terrestrial bipedalism.
Hominin species such as Homo erectus were already nearly as efficient at bipedal locomotion as modern humans around 2.8 million years ago. Bipedalism provided advantages such as freeing hands to carry tools and resources, improving energy efficiency, and adapting to changing environments. The development of reduced nonhoning canines, large brains, and stone tools came later in human evolution.
Reduced nonhoning canines evolved to accommodate changes in diet and social behavior, while large brains and stone tools appeared later in the genus Homo, with Homo habilis being associated with the earliest known stone tool technology around 2.6 million years ago.