On: There’s a 1,200-year-old Phone in the Smithsonian ...

[coldtea]

>Could the purpose of these two gourds on a string have been something else?

Nope, the design and structure of it, simple as it is, are pretty telling.

[qbrass → coldtea]

A single gourd on a string is a musical instrument in several cultures.

I don't think that's the case here, but it might have been how it was invented.