We cannot - therefore, your assumption must be incorrect, in a case of proof by contradiction.
Sports are physical events, where certain biological differences clearly affect performance. Race does involve biological factors besides just skin color, and some scientists have concluded that sub-saharan africans (not just "blacks", but a more specific subgroup) have a leg-length-to-body-size ratio that favors the kind of movement seen in basketball. You will find a similar bias towards taller basketball players - height being a quite clear advantage in the game. Discrimination is in fact allowed when you're discriminating on "ability to do the job" - you see which college-level players perform well, and hire them, and if reality happened to be biased towards a specific group, that's not really a problem.
However, no reproducible study has found a statistically significant difference in mental capacity between humans of different races. There are clearly some people who are smarter than others, but race is not a reliable predictor of intelligence. And since there are no physical differences that make one better or worse at data analysis, seeing any company that does data analysis with a substantially different racial makeup is suspicious. Maybe there's an explanation - it could be coincidence, or maybe another company has a hiring policy that's biased towards asians and hired them all up. Maybe there's a factor being discriminated on that correlates with race - preferring native citizens or permanent residents over those on work visas might give this result (or it might not). Or maybe Thiel's just racist. He hasn't been charged with anything yet, they're just checking to make sure there's not anything illegal going on.