[richdougherty]

Yes, no one's saying that people evolved a predisposition for participating in genetic studies specifically. It'll be some other traits like you suggested. The research is just saying "these databases are not randomly selected and we can prove it using only the database content". This is useful info to keep in mind when using the databases to draw conclusions.

[JoeAltmaier]

I'd be more concerned if other studies didn't have the same genes. That is, is there something special about genetic study volunteers. If not, then we can remove the 'genetic' word from the title. I.e. "People in {any study} database have...'