Is anyone truly 100% British/French/German/Italian/Spanish etc ?

[firemonkey]

Or do we all have at least small amounts of other ancestry?

[rein]

If you’re Irish than you can be indeed 100% British and Irish, as most of them score in the 90-100% range.

[Grace O'Malley]

If you’re Irish than you can be indeed 100% British and Irish, as most of them score in the 90-100% range.

Yes but that is based on modern populations so of course you will match that category very well if they have good samples. It hides a lot of admixture though and any category these modern dna companies uses will include all the people that contributed to that population previously. The reason why people can get varied ancestry comps is because they don't have enough samples or it depends on what algorithms they use. People used to get 100% French & German on 23andMe in the past but they now no longer do now as most people now would be lucky to get 40% French & German. If you have an Ancestry account they are now updating a lot of people's results and because they have much larger population samples a lot of people are losing trace regions and people are now starting to get very large amounts of England & Wales for example. The only problem with dna companies is that they don't have enough samples from places like France and Germany etc. So people from these areas will get very varied Ancestry Compositions and end up with large amounts of British & Irish on 23andMe and England and Wales on the new Ancestry breakdown or have Ireland and Scotland with no known ancestry from there.

So meanwhile people like the Irish will get near 100% British & Irish or 100% Ireland & Scotland and a lot of Europe will be left wondering where they got that Irish / British ancestry from.