I was waiting for someone to bring up Wim Hof. I think he's amazing and pioneering but I think there may also be a genetic component to his work since NW European DNA already gives him a headstart IMO plus probably has neanderthal DNA which was probably well-attenuated with extreme cold.
I wouldn't be surprised at all if there is a genetic component but that's why I mentioned that these attributes have been replicated in his students. But then again the fact that your body can acclimatize to cold or heat is not exactly groundbreaking news. We've known that for a long time.
