Child marriages, including betrothal, has been a part of human culture throughout recorded history. Most had been arranged marriages. While the betrothal of a bride to a groom (more common than the betrothal of a boy to a bride) seemed to be at any age, it was usually held off until puberty. In the case of Mohammad, he married Aisha when she was only 6, but did not consummate the marriage until she was 9. Puberty at such an early age was uncommon at the time, but considering that some of the factors that promote it were there, including eating regularly and a possible genetic disposition for early puberty, due to short life expediencies of the era, make it possible for that to occur. I know of one of my nieces that hit puberty when she was 9.
I'm not saying this is right, but at the time, it was considered acceptable, just like slavery of ancient times was as common as slavery in colonial America.
According to halakha, the legal age of consent for Jewish girls fell between the ages of 3 and 12, although rabbis did urge to wait for puberty. The girls' fathers had to agree to such marriage.
Throughout India, arranged marriages have been common for centuries, often with the girl marrying before the age of five. During those years, the bride lived with her parents until her husband could claim her and consummate the marriage. This was done because of raiders that would attack villages and **pe any unmarried girl (who wouldn't be prone to a venereal disease) but if an 8 year old said that she was married, and could prove it, the thugs would basically leave her alone. I know, I found that one hard to believe, too. The habit is still practiced in out of the way places in the country.
Throughout the Christian dominated world, again, early marriages were common. Prior the Code of Canon Law of 1917, the marriageable age for a member of the church was 7. from then on, including a reconfirmation, the marriageable age was raised to 14 years old for girls and 16 years old for boys.
One of the reasons early marriages were so common and accepted was because it took a large family to work the farms back then. You had to start early, considering that most people died by the age of 40. Depending on the family circumstances, a child bride could marry a man twice her age, and they would still be considered minors by today's laws.
So were our ancestors sickos, or practical?