That's not an accurate description of the research that has been done in the field. There's certainly not "more evidence for the biological side". Mathematical performance on standardized testing is quite similar (
http://www.sciencemag.org/cgi/content/summary/321/5888/494). When people read that study many are quick to point out that there is greater variance for men than for women, however other studies suggest (
http://www.pnas.org/content/106/22/8801) that could certainly be attributed to cultural factors. Just read the abstract:
"Using contemporary data from the U.S. and other nations, we address 3 questions: Do gender differences in mathematics performance exist in the general population? Do gender differences exist among the mathematically talented? Do females exist who possess profound mathematical talent? In regard to the first question, contemporary data indicate that girls in the U.S. have reached parity with boys in mathematics performance, a pattern that is found in some other nations as well. Focusing on the second question, studies find more males than females scoring above the 95th or 99th percentile, but this gender gap has significantly narrowed over time in the U.S. and is not found among some ethnic groups and in some nations. Furthermore, data from several studies indicate that greater male variability with respect to mathematics is not ubiquitous. Rather, its presence correlates with several measures of gender inequality. Thus, it is largely an artifact of changeable sociocultural factors, not immutable, innate biological differences between the sexes. Responding to the third question, we document the existence of females who possess profound mathematical talent. Finally, we review mounting evidence that both the magnitude of mean math gender differences and the frequency of identification of gifted and profoundly gifted females significantly correlate with sociocultural factors, including measures of gender equality across nations."
Let's be clear here though. There are indeed be biological differences between the male and female brain. Females may be better at certain tasks than males and vice-versa. The question is, is there evidence to suggest biological factors could play a significant role in explaining the extremely low amounts of women in science? Consider the fact that even if some biological difference in mathematical ability could be demonstrated, that wouldn't even come close to explaining the disparity. We're not trying to produce Nobel Laureates here, just scientists.