By questioning whether their sources are reliable.
Explanation:
Early historians used unreliable sources to write history. They had to believe mainly on sources which were believed by people. Modern day historians has many instruments and theories to prove an incident of history. Scientific advancements has helped calculate the accuracy of any event. Carbon dating is one of the many scientific advancements helping modern day historians. This test helps them to find out the age of any fossil found, thus giving an accuracy and reliability of the sources which will be documented.
The main way in which the modern study of history challenges earlier histories is that there are so many more sources available, along with physical evidence that has been discovered, that make understand the past much easier than it was previously.
