Does anyone have any experience working someplace where it was all one gender. Then a person of the opposite gender starts working there. How does it change things?
I was once the sole male in a formerly all female optometry office. I was single and in my 20’s at the time. I hate to say it, but on one level I feel like I suddenly acquired a half dozen new moms when I started work there…here, I baked some brownies, try one…oh dear, your collar is twisted in the back, let me fix that for you…you say your date stood you up last night? well, here’s what I recommend you do…
I work in a predominantly female company, in an exclusively female office (except for me). It’s never been an issue, fortunately. The women I work with are people I highly respect and value, and they seem to feel the same way about me–except one, who keeps calling me an ass and punching me when I try to kiss her. But she’s my wife, so I’m used to it. 
But the culture of the company I’m in is almost militantly progressive, so I’m in a fairly unique situation, sadly.
I have worked mostly in all-female environments, and I love it when a man gets introduced into the mix. Too many women with health science & anatomy backgrounds usually makes for too much constant talk about periods, pregnancy & bladder infections…but that’s just my experience, and since I do work in health care, we talk about a bunch of sordid shit that would be highly inappropriate in any other work place. I think if we had more men, the ladies wouldn’t freely yak about their vagina so much, ya know? We have a lot of fun and we laugh a lot, but it does stray into oversharing too often. Our total department has around 30 people, with only 2 men.
I am currently the head of a team of 5 women and we have 1 opening we are interviewing possible candidates for, and I am really hoping for a qualified man. Too much estrogen in the air, and we need a few more drops of testosterone.
I’m often the one breaking in. Most people’s reactions fall under either “oh nice” or “new coworker, hi”. I realized long ago that the guys who have bad reactions are unfailingly trying to protect a weak position; to them, any new person is a threat and one from “the wrong gender” is a bigger one because she/I/he represents a whole half of humanity, in their eyes. I am several billion 
The closest I ever came was working in a daycare.
Guess who was always called when anything heavy needed lifting if anything needed fixed.
I was one of the first female telephone installers in the 1970s. I don’t know what it was like before, obviously. In my experience, all of the women hired, mostly by virtue of a consent agreement (“we did not discriminate and we won’t do it again”), were given extra time and extra training. As in, it was assumed we did not know how to use hand tools.
I first applied in November because it looked like a fun job and there were openings. The interview was strange, because at that time the rule was, for women, wear a dress to an interview. But what about this kind of interview? So I wore the usual interview dress. The interviewer went straight to the point. “You will have to drive around in a telephone truck, can you do that?” Sure. “You’ll have to go into basements and under houses where there are spiders, you okay with that?” Sure. (Lie.) “You’ll have to lift 60 pound ladders, can you do that?” Yes. (Maybe; it turned out you don’t actually lift the ladders and most of them don’t weigh that much. “You’ll have to lift 120 pound cable spools.” Now at this time I weighed like 100 pounds and I thought I might have a problem with that. But I had strong legs. And turns out that bit was bullshit on his part too, along with the ladder thing. So I did not get the job.
In December the consent decree happened, and in January the phone company called me back.
Along with hand tools, the extra training for women included some time in the gym so we would be up to lifting 120 cable spools, which as it turns out, they only weigh that when they’re full, telephone installers don’t usually lift them, and they are only lifted once when full, into the truck. Usually the truck of a cable splicer. So the guy interviewing me was just trying to rule me out. Hooray for consent decrees.
After that things were fine, and then telephone installers started being phased out and guess who was at the bottom of the seniority list?
A lawyer friend said that when women started working at his office how the atmosphere changed. No more smoking. No more bottles of booze in the desks. No more foul language.
Were there any downsides? 
I was only guy in my department for about two years, I kind of enjoyed it. Now they have hired more guys I’m not unique anymore. I miss it.
So how do you think that department changed after you came on board?
Please don’t extrapolate too much from this single example.
For many years, I worked as a security consultant. All the consultants were men and most of them had LE backgrounds. (I did not.) We had an extremely hard-working and smart office manager. She did a lot to help “behind the scenes” when we provided services to clients. The clients we worked with directly were also overwhelmingly male.
The office manager pushed to get more directly involved with clients and was eventually moved up to be a consultant herself. The response from clients was surprisingly negative. They knew that she did not have an LE background (again, neither did I) and they made no bones about the fact that they felt she was unqualified to even try to help them. More than one told me that they didn’t expect her to be able to provide them with any support at all and that spending time with her was a waste. They even mocked the professional certifications she had earned by saying, “I lost all respect for the certification process when they gave her one.”
This went on for about two years. She became a VP in the company, but moved to being more of an in-office project manager. By that time, I had left the company, but I still heard from their clients that they thought it rather silly that she had been sent to them to provide consulting services.
Sad, but true. This was in the 2003 time frame.
Back when I worked in IT, we were an all-male office (except for one lady up front who wasn’t involved in IT). Then, the boss said he was hiring a woman, so we’d have to behave ourselves. We actually had to do a training session, I don’t know what to call it, “sensitivity training”? “How not to be an ass” training? The bit I remember from it most vividly was the trainer asking for change, like, right now, but I didn’t have any, and I told her I have change in my car that I can run and get, but I don’t have any on me. She ran through it with the other people too. Apparently, the point of the drill was, she needed change for the tampon/maxi machine in the women’s restroom, and we weren’t supposed to pry into why she wanted change so badly because it might embarrass her. Really a lame exercise.
Anyway, when the new woman started working there, it was no big deal; we didn’t change much, and she fit right in.