I'm assuming that if I pick random PhDs and hot dog vendors, I will get a higher average IQ from my random PhDs. Are my PhDs strictly greater in IQ than my hot dog sellers? Maybe, maybe not. But will, say, 99% of my PhDs have a higher IQ? I'd bet on that number or something like it.
> No, people from 2000 years are just as smart as you and me.
No, they were not. There were a few geniuses back then, the ones we still read and write books about. All few tens of thousands of them out of billions. But the average was vastly below the modern-day.
The environmental causes alone are legion: lead plumbing, no formal schooling (worth something like 5-10 IQ points), rampant parasitic diseases of every conceivable sort, irregular or poor nutrition with nutritional deficits (protein deficiency damaging early neurological development - low myelination of nerves, iodine deficiency, etc.), medicine that would kill most patients...
Your only valid points are that IQ is not perfectly correlated with success and that it varies within every group. This is not news to anyone who has done even a little reading on the topic.