In Genesis the ages of Adam and his offspring are stated as being very long. Adam lived to be 930 years old. This seems like a long time, why did people used to live so long? Perhaps they didn't. Pre Julius Caesar (Born 100BC) most of the world was on a lunar calender. Most of the old testament's works are dated from around 500-800BC.

Now assuming some sort of error in translation or confusion about calenders occurred, suppose months were translated as years. We can devide everything by 12 (Or pretty close, a lunar cycle is ~28 days). Now Adam's age becomes 77.5, Seth's age becomes 76. Genesis states Adam had his first son at 130, which seems a long time to wait, especially considering no birth control existed for the first two people in the world, but divide by 12 and you get 10 which would be around when he'd first hit puberty.

I don't know of any way to prove this, but when you make the assumption that there was a translation problem all the numbers make a lot more sense, and it would fit that ages would be counted in lunar cycles instead of solar cycles at that time.