Tiwanaku are a pre Columbian native American civilization that existed around Bolivia in South America. I put them in the list because they have left behind some interesting ruins. As I mentioned in another post when I see native American results like that, I think it's from the shared ancestry (overlap) between Europeans and Native Americans from the upper paleolithic population known as Ancestral North Eurasians. ANEs abbreviated. Northern Gaul would not be isolated from Southern Gaul.
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This is a bit of info if you click on Iron Age Briton in IllustrativeDNA. It mention's what I have screenshotted.
This is the study that discusses this large-scale migration from France into Britain starting about 1300 BC :
https://www.nature.com/articles/s41586-021-04287-4
So If you have British Ancestry I wouldn't be too shocked to see that.