A lot of blonde hair
It’s true, here in Poland, we actually have quite a few blonde people. Our genes prove it!
The MAF (minor allele frequency) for the HERC2 gene variant, referred to in the literature as rs1667394, is 61% for the general population (GnomAD v3.1.1), but in the Polish population it is estimated at 86%. This variant significantly increases a person's chance of having blonde hair.
"The Thousand PolishGenomes Project - a national database of Polish variant allele frequencies" is a unique scientific project, the aim of which was to create the first database of genetic variants of Poles and Polish women. The presented results come from this project.
If you are interested of hair genetics:
P.S. Of course, there exists data that is less extensive than WGS analyzes from other populations, but with a much larger sample size, for example in 23andMe or FTDNA collections. In this project, however, we focused only on data from genome-wide projects. Remember that the The Thousand PolishGenomes project is open to more discoveries by other research groups in the upcoming groups, and the presented results are only the tip of the iceberg.