Re: "why Blacks are such fast runners?"
"a 50/50 mix in other countries like India and China" will be news to women in those countries.
The statistics vary depending on exactly what you count as "working in tech" but excluding virtual slave labour assembling iPhones the figure for women is anywhere between 3% to 20%. A long way short of they mythical 50/50.
Genetics are likely to be a small factor in differences in career choices but it cannot be argued that gender isn't a factor whether the decision is to have a career as a Child Minder, Kernel Coder any of a thousand other career.
It is actually hard to find many careers where there isn't a difference to be found when it comes to gender balance.