A sentence fragment...
It does not sound right, therefore it is not complete (fragment). Run-on sentences are complete, yet they are extended to much.
Answer:
He embraced me then,
But later he could not keep up,
How will I let go?
Ambiguous.
It will be an "ambiguous" ending.
Polygamy began to end when agricultural development and settling got introduced. During the nomadic non-agricultural period, polygamy was common and people were not tied to a single person.
Waterways were among humanities first major transport routes. Whereas oceans acted as barriers in ancient times, in modern times they have been highways of travel and trade.