Originally Posted by
Longbowman
3) So why are they so often cited in human genetics?
Because they're the only genes automatically handed down father-to-son, and mother-to-child, excluding mutations, which makes them useful for identifying racial groupings. So if 80% of Britons are R1b, then R1b becomes associated with Britons. But, even assuming YDNA chomosome X is exclusively Finnish in origin, if someone has YDNA clade X, all it means is 1 great great great great great etc. grandparent was Finnish - and thus YDNA isn't hugely relevant in determine the race of an individual. Similarly, not being clade X doesn't mean you aren't Finnish, it just means your great great etc. grandparent wasn't Finnish. The remaining 99%+ of your makeup could easily be Finnish.