This is the other thing I hate about the diet section of this forum: people don't know how to READ in this section! I already said that what works for me is accutane, BP and AHA. Now I just use BP face wash every night, let it stay on my skin 2-3 minutes and wash off and I'm 100% clear.
I did what you suggested last summer and oh boy I was fucked! I had so bad acne, it was a fucking nightmare.
I see that alternativista has ran back to the troll forest when her theories got proven wrong.
You seem to be suggesting that the incidence of acne has remained stable over that last few thousand years. If it was purely genetic and there was no interaction with environment, this would be the observation. This is not the case, so you're wrong. You can question which specific environmental interaction is a trigger of acne. This is still a subject of a lot of research, and there is probably no one answer.
Acne is a display that something is wrong within your body. Think about smallpox; red dots on your skin warn others to stay away; your immune system creates them to decrease the likelihood of spreading whatever it is you have. There are many diseases that result in similar rashes or dots and for the same reason, and in each case the dots are not a manifestation of the disease, but rather a manifestation of your immune response. With acne, your body is warning others to stay away, because something is wrong.
Now let's take an evolutionary perspective. Would this trait of warning others to stay away during our most crucial social years be evolutionary beneficial for everyone to have? No, of course it wouldn't be. The moment someone comes along who does not suffer from acne in a population where all of the individuals innately have acne, their genes would be selected for. They would get more mates. They would have more social bonds and a bigger social network. They would have more resources, and more people to watch their back. The acne gene would disappear very quickly - unless it was meant to keep others away for a good reason (one that increases net fitness), and was triggered only in certain circumstances.
And so by evolutionary logic, you're also wrong. Of course, could have just pointed out that hunter-gatherers do not suffer from acne, teenage or otherwise, but now you see some of the logic behind that observation.
In short, it seems incredibly shortsighted of you to suggest that acne is purely genetic and has no environmental triggers or interactions. More importantly, though, I think it's best to remember that nobody has a cure for everyone; doctors have cures for some, and diet has cures for others. Once we find the cause of acne (which we have yet to do, after all these years), we'll be better able to determine just what exactly is going on.