Bear in mind that people aren't averages. On average more boys than girls excel at math, but no one told that to the chair of my university statistics department, or to my PhD advisor--both very talented mathematicians.
It is true that there is much more male than female players, actualy there are around 400 000 active male players, and around 60 000 active female players, but the best answer on this we can get if we take average ratings.
According to www.chessrating.info the average rating of all male players is: 1775 and average rating of female players is 1576, so it's clearly that male chess players are better than female!
These arguments about having less interests from girls to play doesn't work. Women have less interests because precisely they are more right brained. The right brains is responsible for immediate analyses, not anticipation form past experiences, therefore chess becomes boring for women and you end up with less women signing up to your classes.
The two questions that seem to torture so many of the boys on Chess.com: "Why are girls so icky and dumb?" and "I wonder what sex with a female is like?"
Stop bringing back this thread. Who cares. Just play chess.
The main reason why there are less girls than boys playing chess is the inequalities propagated by society, the family upbringing and the school system. It is unfair and will only change when society starts treating women with more equality and without gender biases. Theoretically, if you could create a just society where boys and girls believe they can do anything they want just as well, then girls and boys would succeed equally well.