There are a few studies showing links between cannabis use and infertility in men. Smoking cannabis is a double whammy, because tobacco use is a leading cause of erectile dysfunction.
> what I would assume is pretty consistent pot usage over the last, say, 50 years.
That's a big assumption. I'd be interested to see any numbers to support it. Certainly in the UK it feels like people smoke more, smoke more often, and start earlier. But I don't have any numbers, this is just my opinion. I'd also be interested to see if modern cannabis actually is stronger than cannabis used in the 60s, 70s, 80s, etc.