Answer:
These statements apply:
Scientists might find new sites with human artifacts, thus providing new evidence.
If scientists find human artifacts in new places, such a finding would likely change archeological theories about the first migrations to North America.
Scientist might develop new technology that helps them assign different ages to existing artifacts.
If new technology is used to assess the time period of certain artefacts, and that technology determines that the time period is different, then what happens is that the time period itself to which archeological evidence was tied changes, meaning that the dates previously established have to be revised.
Scientists might come up with new theories using existing evidence.
If scientists can developed new sound theories using existing evidence, then it is likely that the dates previously set are modified.
