What is then most important change brought by the development of language?

That's a fascinating question with no one definitive answer! The development of language is a complex and profound event in human evolution, and it has had a massive impact on many aspects of our lives.

Here are a few contenders for the most important change brought by language:

* Enhanced communication and collaboration: This is probably the most obvious and immediate effect. Language allows us to share complex ideas, emotions, and experiences with others, fostering understanding, cooperation, and social bonds. This enabled humans to work together in more sophisticated ways, leading to advancements in technology, culture, and societal organization.

* The development of abstract thought: Language provides us with a symbolic system to represent concepts and ideas. This ability to think abstractly enabled us to conceptualize past, present, and future, plan for the future, and engage in complex problem-solving.

* The rise of culture: Language is the foundation of culture. Through language, we pass down knowledge, stories, values, and beliefs across generations. This allows cultures to develop, preserve their traditions, and evolve over time.

* Increased self-awareness: Language helps us understand and label our own thoughts and feelings. It allows us to reflect on our experiences, form identities, and develop self-awareness.

Ultimately, it's difficult to pinpoint a single "most important" change because each of these aspects is interconnected and contributes to the overall impact of language.

Perhaps the most important change is the transformation of human consciousness itself. Language allowed us to break free from the constraints of immediate experience and explore the world in new ways. It opened up a vast universe of possibilities for thought, creation, and connection, shaping our understanding of ourselves and the world around us.