he knew, first hand from his work at the 1000 genomes project. there is no way in this world you can miss these patterns when you work all day with samples of all races genes. even before all this scientific proof was available, as someone already mentioned, it was really common sense. people are fixated with appearance. from an evolutionary perspective, you want to choose a mate who looks like you, behaves like you. and when you screw up, it becomes painful
Canada