A common argument against past human achievements – that they are either fraudulent, or the result of superhuman intervention – is the supposed impossibility of those achievements. The Nazca lines, the pyramids, astronmical discoveries, Stonehenge etc. A whole field of woo, starting with von Däniken’s Chariots of the Gods? is based on the premise that past humans could not have been clever enough to do things, simply because we, today, don’t know exactly how they did it.
The argument devolves to “I can’t figure it out, so how could they figure it out?” or, more simply “Nobody in the past could possibly be smarter than me.”
That’s why I love this TED video. It shows a simple device invented millenia ago, but I would wager far fewer than 1% of people alive today – especially in the developed world – could figure out how to make one.