In a conversation in r/history on contact between Han China and Rome, the Xiongnu came up, and many people wanted to know who they were, where they came from, and whether the Turks or the Mongols or the Huns or whoever were their descendants. Wikipedia gives me a host of cited theories on their origin, but is otherwise pretty bare bones.
What are the current leading theories, and how much support do they have? Is there evidence for a connection to any later peoples, such as the Turks or the Mongols?
I was just reading "How Rome Fell" by Adrian Goldsworthy and he says we just can't know, the theories are more conjecture than anything. Actually, the lack of information we have about certain aspects of the latter centuries (and even before) of the Roman Empire is something he brings in again and again. He even makes a comparison that if we had the same level of informatioan about the 20th century as we have about the 3rd we might think that Germany and Japan had a continuous period of prosperity and that the two world wars were not that big of a deal.
It seems the one thing we can be sure is that they were very alien to the romans, who were not used to see people like them.