Bereshit begins with the first 6 days and the Shabbat. The assumption is then that after that day, Mankind kept track of the day of the week all by themselves until today. Are we sure that no one ...
The Torah tells us (Genesis 4:17) that Kayin built a city and named it after his son, Chanoch. If Chanoch was only of the third generation of humans, how was the total human population at the time ...