Follow-up to that other question about a 1900 historian's possible "misconceptions" from our point of view. I know technology played a big role in terms of our gaining raw data about ancient history, but I don't know what was discovered when. How big would the gap between our understanding of ancient cultures and the 1900 historian's be?
I don't think it's an exaggeration to say that virtually every aspect of archaeology has been overwritten in the century plus since 1900. Technical improvements in optics, chemical analysis, and computing have certainly contributed substantially to our ability to analyze archaeological data, but the greatest improvements have come from the intellectual development of the field rather than the technical.
Yes things like carbon dating and genetics exist now, but it's worth considering that the majority of archaeological research still uses tools that would have been just as capable a century ago. What's changed is the intellectual context all these tools and techniques exist in. We're still using excavation data from the 19th and 20th centuries at Chaco canyon and yet almost all of the interesting results concerning the canyon were published after 1980.
Just to list some of the developments that have appeared since 1900:
Past societies had economies
Genetics is not the same as culture. Past archeologists used to claim migration for every instance of observable cultural change. The reality is that sometimes people changed without being invaded by barbarians.
Archeology is no longer (directly) an element of state sponsored colonialism. I still criticize anthropologists / archeologists for not being cognizant of the political ramifications of their research, but the field has dramatically improved.
Resistance and agency are actually important now. This has had huge implications in non European archeology.
Archeologists are beginning to treat the subject of change. This is one of the big future challenges, but past archeologists simply had no conception that it was even a problem.
We've gotten somewhat away from the major Western assumptions, like teleology and gender when historical people. Despite the public unpopularity of some of these ideas, they've been incredibly useful.
Entire books have been written on this subject, but hopefully that gives you some overview of how archeology has developed. The technical innovations have been cool, but these intellectual ideas have had so much more impact on our ability to interpret even the data we already had.