Apropos of this and our understated relatedness to one another, I was reading about the role of GEDmatch in (inadvertently) solving criminal cases (and how it's become the go-to for law enforcement in the US). Despite a fairly modest pool of genetic data that only covers around 1% of the US population (and predominantly white, Europe-derived Americans who pay for services like 23andMe), relatedness makes it very powerful (on average any given individual has up to 300 third cousins). Basically, they exploit the innocent upload of genetic profiles (these are SNPs, not the more specific STRs used in law enforcement databases) by relatives (often distant) by building a family tree. SNPs can also reveal things like ethnicity, hard colour etc. as they can fall within genes (STRs, on the other hand, are more purely genetic markers).