Infer: what is the relationship between the evolution of bipedalism, the increase in cranial capacity, and the decrease in tooth and mouth size of hominins? (hint: as cranial capacity increased, the use of sophisticated stone tools became more common.)

When the organism become bipedal, they walk with 2 legs so there are 2 arms that were unused. Some of them try to use that hand by grabbing stick or stone, leading to tools. They start to think more to develop tools and their brain capacity become increased.
The ability to use stone tools will help in food digestion since it can break the food easier. This reduces the needs for bigger teeth/jaw.

Organism, organ system, organs, tissue, cells