Why would the cold weather hypothesis be a theory that only goes back 200 hundred years as you claim? Just looked at some of the papers on the topic and it's tracking the human migration out of Africa and tracking when the first tools of various types were found and when. In more modern time the Norman invasion of France is about 1000 years ago, followed by England, not to mention the harsh conditions the Mongols were under (-40c degree winters) for about 3k years before conquering China - seems that led to a good bit of genetic spread.
Seems you're arguing that there are no differences between IQ in populations regardless of immigration patterns/conflict/harshness of the environment? If that's your claim please state it. My claim is that there are observable differences in populations of people, that are observable in the prosperity of regions and cultures, that are visible between nations and cultures, and that IQ distribution is highly likely to be root cause - or as close as we'll come to measuring the driving cause successfully. Evolutionary forces likely drove those observable differences.
It is simply an area that is taboo to research in depth because of how uncomfortable it makes folks whose morality is tied up in some form of cosmic equality/equity.
More over, I think it's imperative we study this vigorously and find truths no matter how uncomfortable that is for segments of society - particularly if we want to find interventions that work to better everyone's lot in society. Otherwise you'll spend lives and treasure to make no meaningful improvements to the conditions of people country/culture.
There aren't many Ashkenazi Jewish sprinters in the Olympics, is it so far fetched to believe that there might be more than sprinting ability differences between populations? Should these differences not be studied to better understand and improve society?