Passage Summary: The author suggests that because the Silk Road was easy to travel, people probably used it for trade long before 200 B.C., especially since we know humans were already moving into China via similar paths a million years ago.

Conclusion: Trade routes between China and the West likely opened much earlier than currently believed.

Reasoning: The same geographic features that made the Silk Road a good trade route would have made it a good path for ancient migrants, and we know people migrated to China a million years ago.

Analysis: The statement about the million-year-old migration serves as a premise. It establishes that the path was physically used by humans in the distant past, which supports the idea that the path could have been used for trade earlier than the traditionally accepted date. It provides historical context to show that the 'attractive route' wasn't just theoretical—it was actually traversed.