How did the Nazis figure out whether a person or community is 'Aryan' or not?

It was all bullshit the Nazis made up as they went along. Trying to cast it in real scientific terms is a waste of time.

Ultimately, what made a group of people “Aryan” or not came down to how much they wanted them to be “Aryan”.

Ja, well, Helmut, it’s very simple. Those hot leggy blondes are actually not Slavs at all but are, in fact, Aryans who got Slavicised. We need to rescue them from the pit of subhumanism that surrounds them by immediately giving them Aryan status!

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And then we get sexy time with them!

Poles are “ugly, subhuman Slavs” but hey, Hermann, have you noticed how hot and blond those leggy Polish chicks look? They don’t fit our “subhuman” model at all! İn fact, they kind of look like our Aryan ideal personified!

If the Nazis wanted someone to be “Aryan”, they made up some cock and Bull story to justify it. If they wanted the opposite, they could be equally inventive in assigning someone to “Untermensch” status.

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They used their “spidey sense”.

Nazi racism was not actually scientific, it was just a load of bullshit with a thin patina of “science-y” garwharbl to justify what was basically a totally ideological belief.

And then we get sexy time with them?

Does the U.S military really prosecute military staff for cheating on their spouse, or do they close one eye if the cheating does not involve other military personnel since adultery is fairly common? Adultery is illegal in U.S military