I mean a scientist could easily prove it with today's knowledge its more it would be a lot of time for very little pay off since she's Japanese not European and also not a scientist she's a agriculture school attendee.
So, looking at the map, they showed the last chapter and the possible capitulation of the Sanada to Oda authority, the only major clans left are the Shimazu, Hojo, Date, and Chosokabe.
"The Nagao were the Kasai (Head retainers) of the Uesugi clan, and were the Shugodai (vice-Governors) of Echigo, Kozuke, and Musashi province."-Wikipedia
So I'm guessing that they are the hostages sent by Usegi as a declaration of his loyalty and submission. Since Usegi is not actually a born...