Introduction:
The development of the skull size and distinctive jaws of early humans has been linked to the tool-making ability that they possessed. This ability allowed early humans to hunt and gather food more efficiently, leading to a change in their physical features over time.

Development of Skull Size:
The evolution of the human brain is one of the most significant factors in the development of skull size. Early humans had smaller brains than modern humans, but their brains were still much larger than those of their primate ancestors. As early humans began to use tools, their brains began to grow larger, which required changes in the shape and size of the skull to accommodate the increased brain size.

Distinctive Jaws:
The distinctive jaws of early humans were also a result of their tool-making ability. The use of tools allowed early humans to process food more efficiently, which meant that they needed less powerful jaw muscles. Over time, this led to a reduction in the size of the jaw muscles and a change in the shape of the jawbone.

Impact of Tool-Making:
The ability to make tools allowed early humans to hunt and gather food more efficiently, which led to an increase in the availability of food. This, in turn, allowed early humans to devote more time to other activities, such as socializing and developing culture. As a result, the development of tool-making had a significant impact on the evolution of early humans, leading to changes in their physical features and their way of life.

Conclusion:
In conclusion, the development of skull size and distinctive jaws in early humans was closely linked to their ability to make tools. This ability allowed early humans to hunt and gather food more efficiently, which led to changes in their physical features over time. The impact of tool-making on the evolution of early humans cannot be overstated and remains a significant area of study for researchers today.