Yes plus we didn't have any lighting back then. You had to get home before sundown because otherwise you would not be able to find your way back. We could not pull 14 hour work days like we can today. You may be able to get away with an extra hour or two in a moonlit night. But that was rare... Especially for work that requires attention to detail.
Our ancestors had to deal with extremely hard times and slavery was the main way they worked around much of that hardship. They really didn't have many options. It was either that or you, your family and your village would starve 4 to 6 months of the year every year.