When I was still in, this made me doubt the bible most. How could mankind be only 6000 years old when science and aerchology prove wrong? I sincerely wanted to solve my doubts and asked other JWs how I could explain this to a householder. This is what they answered:
"I wouldn't go into this. Just discuss with the householder what you have in common." - a regular pioneer
"There are other things that prove the bible is God's word." - a young sister
"Science can be wrong. When they dig out things from the earth, it could be full with radiation and that changes everything." - my mother-in-law
(So that it is not 100,000 years old but only 20,000, but it's still older than 6,000 years.)
*rolls with eyes* "Do you believe that this is the truth?" - an elder