Tartan Tales - BBC TV series

[OC Richard]

...non-native looking sheep. These animals were reputed to be relatives of survivors from some of the wrecked Spanish Ships from The Spanish Armada (1588).

Using isotope analysis, the individual sheep born in Britain would show up as being born in Britain regardless of where their ancestors came from.

That's the cool thing about that test: it shows where an individual spent the first years of their life, regardless of where they travelled to later in their life. (It doesn't test ancestry, that's the DNA part.)