The Younger Dryas theory supporters is controversial across multiple disciplines because it challenges the idea that human progress has always been linear (gets better over time).
Some believe that ~13,000 years ago, humans were highly advanced, but a massive flood (Younger Dryas) wiped out & reset civilization.
Supporters of this theory often point to two things: nearly all major religions reference a great flood, and there’s a current lack of understanding how ancient megalithic sites were built with tools thought to be available at the time (primitive bronze tools, etc).
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Unfortunately, it seems like folks from both sides of the topic talk-past each other ... and at least I haven't seen a balanced debate on the subject. If someone has seen a balanced assessment, please share.