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It seems as if technological advancements in the GOT is unduly slow if it occurs at all. Humans appear to have the same level of weapon and transportation technology etc. in the current timeline (Jon Snow/Aegon Targaryean as King of the North) as they did prior to the original Long Night which occurred thousands of years ago. Matter of factly, there appears to be no technological advance whatsoever with the possible exception of the Scorpion and really that is just an upscaled bow and arrow. I leave Valerian steel out of the conversation because it is metal enhanced by magic.