Final answer:
Language is considered the hallmark of humanity and has played a significant role in human evolution, social cooperation, and alliances.
Step-by-step explanation:
The hallmark of humanity that has played a significant role in human evolution, social cooperation, and alliances is language. According to biologist Mark Pagel, language is a piece of "social technology" that allowed early human tribes to access a powerful new tool: cooperation. Language enabled humans to communicate, share knowledge, and coordinate complex tasks, leading to the formation of social groups, increased cooperation, and the development of alliances.