The game-changing behavior that the earliest hominids, like Australopithecus, had was:Group of answer choiceshunting.tool making.bipedalism.speech

To determine the game-changing behavior of the earliest hominids, particularly Australopithecus, we need to consider the evolutionary significance of their attributes.

1. Bipedalism: Australopithecus is notably recognized for walking on two legs, a fundamental shift that allowed them to travel efficiently over different terrains, freeing their hands for tool use and carrying objects.

2. Tool Making: While Australopithecus showed some rudimentary tool use, it is not primarily credited with extensive tool-making innovations like later hominids.

3. Hunting: While they may have scavenged or hunted, Australopithecus is not primarily characterized by organized hunting.

4. Speech: There is no conclusive evidence that Australopithecus had developed speech as we understand it today.

Conclusion

The most significant and defining behavior of Australopithecus was bipedalism. This adaptation laid the groundwork for future hominid developments, including more advanced tool-making and social structures. Thus, the correct answer is bipedalism.