Complex sentence: The Native Americans at first participated in the harvesting of the Pampas deer pelts for sale, and in spite of that, the deer population stayed strong until the Native Americans of those countries were defeated by European settlers.
Split into simpler sentences: The Native Americans at first participated in the harvesting of the Pampas deer pelts for sale. Despite all that, the deer population stayed strong until the Native Americans of those countries were defeated by European settlers.