Jason Crawford is maintaining this list on Roots of Progress, an archive of inventions that seemingly could’ve been uncovered earlier than they were, based on what precursor knowledge would’ve been required. This one about stirrups is wild:
Humans domesticated horses in ~4500 BC, but stirrups were not invented anywhere until like ~200BC (4300yrs), and did not show up in Europe until the Middle Ages (from central Asia)
It’s fascinating how there aren’t even clear explanations of why these took the time that they did to discover. It points to the random, serendipitous, evolutionary nature of innovation. Many things with little to no prerequisite breakthrough in materials, processes, or manufacturing techniques just aren’t run across for centuries, or sometimes have social or cultural factors obscuring them.