Comment by exoverito
Continuum fallacy. Might as well claim that there's no such thing as blue or violet, since there's a gradient between them.
Also you can establish homogeneity using genetic analysis such as the fixation index. Unsurprisingly, Swedes and Finns are extremely closely related.
https://en.wikipedia.org/wiki/Fixation_index#Autosomal_genet...
There are many possible metrics to measure heterogeneity, such as linguistic and religious diversity, variations in value systems, etc.
Then again if you look at the continium as something multidimensional. It is easy to make everything either a very specific hetrogenity or a big homogenic pile. The greatest fallacy is the group think, you can always create groups of people and that was the point. Given a bit of encourgement the dividing lines will shift. I have personal experience from work about this and I think some of these meaningless work things we do are there for a reason.
Understanding that we are hetreogenic is hard.