The causation is in the past. Up until about 500 years ago there was little to no gene flow between a number of major population groups. Obviously there has bee

The causation is in the past. Up until about 500 years ago there was little to no gene flow between a number of major population groups. Obviously there has been subsequent hybridization, but we can detect that too. The largest pre-1492 hybrid groups I know of are central Asian for obvious reasons, like the Uyghur people. Last I checked you can’t legally have children with anyone you want in any jurisdiction. You have to get consent and that’s often withheld on the basis of apparent ancestry. Cultural and social factors also make it less common than it would be by random chance. Elizabeth Warren tested out something like ~1/64th Cherokee I thought? And thanks to the wonders of meiosis you could genealogically have relatively recent ancestors of some group without any genetic markers.