Complex sentence: Some archaeologists contend that the ancestors of the Piscataway came to the Potomac River region roughly ten thousand years ago, and coalesced into a nation comprising numerous settlements sometime in the fourteenth or fifteenth century.
Split into simpler sentences: Some archaeologists contend that the ancestors of the Piscataway came to the Potomac River region roughly ten thousand years ago. Historic bands coalesced into a tribe comprising numerous settlements sometime in the fourteenth or fifteenth century.