Interesting article

An article about women leaving tech fields in their thirties and forties, related to recent discussions. The article's main point is good and seems pretty sound to me, but there's a line that's tossed in about "the hostile macho cultures — the hard hat culture of engineering, the geek culture of technology or the lab culture of science" which doesn't get any further discussion. What are your impressions or experiences of that, and why is it one of "[t]he top two reasons why women leave" work in STEM fields?

Ganked from dracodraconis.