In what century did the Great Silk Road through the Steppe begin to operate and when – the Path of Spices across the seas?

In what century did the Great Silk Road through the Steppe begin to operate and when – the Path of Spices across the seas? Why didn’t this happen at the same time?

The Great Silk Road began to operate without interruption at the end of the 3rd century BC, when China and the Eastern steppe were united and “ordered by the powerful Han and Hunnu powers, who concluded an agreement on peace and trade. The Spice Route began to operate after the coastal In the cities of India and China, the class of merchants grew and professional sailors and shipbuilders appeared at the end of the Han era in China and the Kushan era in India in the 2nd century.