If you want to know if your kid is going to be fast, the best genetic test right now is a stopwatch. Take him to the playground and have him face the other kids.' Foster's point is that, despite the avant-garde allure of genetic testing, gauging speed indirectly is foolish and inaccurate compared with testing it directly - like measuring a man's height by dropping a ball from a roof and using the time it takes to hit him in the head to determine how tall he is. Why not just use a tape measure?