Answer:
Scientists usualy use a method of asking around witnesses, then make a hypothosis,and then build onto that hypothosist by asking around for info. Talking to direct witnesses would be hard scense it happend quit some time ago so instead the search for proof to lay a foundation of facts and realy just build from there. After the foundation is set depending on how l0ong ago it happend, the longer it will take to find the answer. So they don't realy know because there is a sertant point were if it was so long ago that the info is not valid, and it is just rumors and guesses, the question becomes difficult to solve. So they realy don't know that what they were told was accurate, because over a large amount of time things can change the stories will shift, and sometimes they will change commpleetly, so they have tno garentee that what they have been told is true.
Step-by-step explanation: