Previously I wrote about why polygyny is not only NOT unbiblical, but it was regulated, allowed and practiced by many of the Old Testament patriarchs. But what about the biological case for polygyny? Did God design men’s bodies for polygynous relationships? What about the marriage of young women to older to men?
Imagine that you were able to take a time machine back to a time in human history around 3000 years ago, deep in the Middle East. You meet a traveler who says he is coming back from a trade journey for his master. You ask him about how he became a slave and he tells you that his parents were in poverty, and that they traded him to his master for some cattle. He says this helped his parents to come out of poverty and to build a life for his other siblings.
He asks you to come meet his master. He tells you that his master was a great hero to his nation, and he is a kind and generous man, a man that worships the one true God. In the distance you can see what looks like a small village. You see what seems to be a celebration of some kind so you ask your companion “what are they celebrating?”
He responds that his master is getting married. As you come closer he points out his master and his bride to be sitting on the ground beside him. The man appears to be his mid-40’s while the girl sitting next to him looks no more than 14. This must be a mistake.
You ask him again – “that girl is his daughter right?” He responds – “No she is his bride to be. My master is very excited, she is his 15th wife and he is hoping she will give him his 70th son!” After wiping the shocked look off your face, you ask you’re travelling companion one more question – “What is your master’s name?” He responds – “My master’s name is Gideon”.
The story I have just given you, while fictional, is based on a true Biblical character and based upon what we know of the culture and times most likely happened (minus the time traveler with one of Gideon’s slaves- LOL).
“Now Gideon had seventy sons who were his direct descendants, for he had many wives. His concubine who was in Shechem also bore him a son, and he named him Abimelech. And Gideon the son of Joash died at a ripe old age and was buried in the tomb of his father Joash, in Ophrah of the Abiezrites.”
When does a girl become a woman?
While culturally we consider a girl to become a woman at the age of 18, biologically speaking, adulthood is reached when sexual maturity is reached. Before the modern era, a girl became a woman when she experienced her first period (usually around 12 or 13), she was then eligible for marriage and usually her father had her married off not long after this.
Lucien Deiss in his book “Joseph, Mary, Jesus” writes:
“How old could Mary have been? Young girls usually were betrothed as soon as they became a woman. It was believed they reached puberty at about twelve or twelve and a half. Boys it was believed reached the age if puberty a year later. Marriage could take place one year after puberty a year later. In general, it was held that men could wait until the age of eighteen or twenty before marrying so that they could have time to build a house and plant a vineyard.”
In “Jesus of History, Christ of Faith” we read:
“The women normally married as soon as they were physically able to bear children, which the Law defined as twelve and a half years of age.” 
Rev. Dr. Eugene Weitzel stated this about the Jewish view of early marriage:
“As we noted above, the Jews clearly understood that the first command that God gave to Adam and Eve was “increase and multiply” (Gen 1:28). In fact one rabbi firmly believed that “A bachelor is not truly a man at all.” Furthermore, celibacy was looked upon as an anomaly, almost a disgrace. Now keep in mind that Jesus Christ, a devout, practicing Jew who dearly loved his Jewish faith, grew up with this view of celibacy. He also knew that his people believed in early marriage. Many rabbis, even during Jesus’s time, taught that eighteen was the ideal age for marriage for a man but certainly not later than twenty-four. He knew too that girls were ready for marriage as soon as they were physically ready to conceive and bear children, which according to the law was twelve and one-half years. Mary, the mother of Jesus, was probably no more than fourteen years old when she gave birth to the Son of God.” 
Zvi Yehuda in his book on Jews that came to Iraq from all over the world for over 400 years writes:
“Where traditional family structure was unchanged, Jewish girls were betrothed by their parents at age 9-11 and married at age 12-13. A Jewish girl who reached the age of fifteen and was still unmarried was considered an old maid with no chance of a husband. A girl bride was not asked for opinion in choose her mate and parents occasionally married off their daughters to men dozens of years older than the bride.” 
The evidence is clear. Both in Jewish tradition and over historical accounts we know that Jews married their daughters off young. Why? Because of God’s first command to mankind to be fruitful and multiply. Men needed more time to prepare a home for their wife – but women as soon they became women(had their first period) and passed the age of 12 were usually betrothed or married and most likely had their first child by the age of 13 or 14.
Teenage mothers were the norm before the modern era
As we have previously pointed out, most scholars believe that Mary was 12 to 14 years old when she was espoused to Joseph to be married. They believe she would have been between 13 and 14 when she gave birth to Jesus. While the Bible does not state her exact age, if she were older it would have stated this as it did with Elizabeth (the mother of John the Baptist). Since the Bible makes no mention of her age, then it is assumed she would have been in the normal first child bearing age of women in that era, which would have been around 13 or 14. Joseph is thought to be a bit older than her (perhaps in his mid-20s or older) because he died well before Jesus’s ministry and Mary was a widow.
Just a note – if you look online there are a few Christians (but a small minority) that have tried to argue with the notion that Mary was a teenage mother and instead argue that she was at least 20 years old as this was God’s age of accountability and God would not have asked her to carry his Son at such a young age.
There are few problems with this theory of Mary being much older. The first problem is that first time mothers in their 20’s were considered to be older mothers, and the Bible would have said something about her older age, like it did with her cousin Elizabeth if she were in her 20’s. Another problem with the magic “20” number is that in most instances of the Old Testament this applied to men being fully accountable, not to women, and even in the one instance in the book of numbers where men are not specified, it does not specify women either, so the assumption always goes to it talking about men aged 20 or older.
Women were accountable to their father as long as they were in his house. He could override any decision she made, financial or otherwise while she lived in his house. His authority over her then transferred to her husband when she got married.
Some Christians want so desperately to believe, against the evidence of historical and cultural data we have of the period and location, that there is no way Mary could have been a 14 year old mother. But this starts with their pre-conceived notion, based upon our modern western culture we have all been brought up in, that marriage of girls at such young ages is an immoral act.
Bearing and Rearing Children is a young woman’s game
Biologically speaking, a woman’s best time to conceive and bear children is from the time of her first period (for most girls between age 12 and 13) and age 24. After age 24 chances of birth defects and problem pregnancies begin to rise. At age 30, a woman has used or lost 90% of the eggs she will ever have and this is why women in their 30’s typically have a much more difficult time getting pregnant.
The reason that God designed a woman to have children at a younger age, as opposed to an older age(like 30s and 40s) is because of the extreme stress that is placed on the body during pregnancy, as well as the energy and physical stamina that is required to care for and wean a child in their younger years.
What about Sarah and Elizabeth in the Bible?
Yes there are few instances of God miraculously causing older women to conceive, but this was by no means the norm of his design. We cannot take these two special cases and try to make a doctrine that God intends for women to wait until their older years to have children.
“I will therefore that the younger women marry, bear children, guide the house, give none occasion to the adversary to speak reproachfully.”
I Timothy 5:14(KJV)
A teenage girl might physically able to bear a child, but she is not psychologically ready
This argument does stray a bit from what is strictly a biological topic, but I think it needs to be addressed. I completely agree that most teenage girls in our culture and time period are not psychologically prepared for having children. But that is because our culture babies children in ways cultures of the past did not.
In Jewish tradition, a boy began his journey to manhood at the age of 13, and a girl began her journey in womanhood at the age of 12. While boys were not fully responsible (for taxation purposes, and conscription purposes and some other legal purposes) until they reached age 20, they were in many ways treated as men from age 13 on. Since women did not have the rights men did, a woman was a full woman at the age of 12 and her status and rights did not change from that point forward.
A young 12 year old girl would have witnessed births by many women by the time she reached 12 and would be fully aware of periods, child bearing and birth long before these things happened to her. She would already have been learning about child care well before she reached puberty. Her whole life would have been leading up to the time when she could finally marry and have children of her own.
So in many ways, a 12 year old girl in pre modern times would have had the maturity level of what many 18 or even 20 year old girls have today.
Also we must keep in mind that before the modern era, families took care of other and were much closer. So when a 13 or 14 year woman had her first baby, her female relatives, whether they were cousins, or aunts, or even her mother were all there to help her learn the ropes of motherhood. Today the tribal family structure has all but been eliminated.
Men can father children at any age beyond puberty
Unlike women who ovulate once a month, and are only fertile for about 5 days, the typical man (unless he has a medical condition) is in essence “fertile” every day. A man completely replenishes his sperm every 24 hours. Before recent research, doctors used to tell men to wait every other day to have sex with their wives during her fertile period. Then they discovered that is was in fact better for them to have sex every day, as all the sperm is at its best every 24 hours or so.
A man since he was not responsible for caring for the child, but for the teaching and disciplining of the child, did not need to have the physical strength and endurance that a woman needed in her duties of child rearing, and this is why a man has no expiration date on his ability to produce children.
The fact of God’s creation in human biology is, men are built for fathering multiple children with multiple women at the same time. They are also built for fathering children with multiple generations of women, as their first wives age and cannot have children, they can continue fathering children with younger women.
This is why men have such a stronger sex drive and can compartmentalize relationships with multiple women, much better than the average woman could with multiple men. Not to mention that a man has a never ending supply of child producing sperm. On the other hand, women are designed with a shelf life when it comes to having children. How else do you explain the extreme disparity between the male and female reproductive systems?
Am I advocating polygyny and marriage to young girls in our day and culture?
As I said before in my other posts on polygamy, I am not a practicing polygamist, nor am I telling Christians or others they must turn to a life a polygamy. I am also not advocating for men to start looking for under age old girls to marry either. So please don’t waste my time with straw-man arguments saying that is what I am advocating for in modern American culture.
My daughter is 12 and I could not imagine her being married at such a young age. The reason for this though, is because of the culture I have been raised in, and the culture I have raised my daughter in, she is immature and not ready to be a wife and mother because our culture, and my parenting, have taught her it is OK to be a child for another 6 years or so.
But if I were to see a culture in another part of the world, where boys and girls were raised as they were in old times, and they had the maturity and depth of those people at such a young age, I would not judge those people.
How does all this apply to us today?
After reading all this, you might say – “so what if before modern times women got married and had babies way younger, and men had many wives – that’s not how are society is structured today, so how does any of this apply?”
There really are two issues here that apply to our modern times, and in this post I will only address one of them, as I believe the other issue merits its own post.
The first issue – the fertility crisis that world will soon be facing in the coming century. In most modern countries, because women are waiting so long (average age of first time mothers is now around 26 in highly westernized countries) the birthrates in these countries among the indigenous populations has plummeted. Many European countries are far below replacement levels (just having enough babies to keep their population stable) and even the US population only keeps a modest growth because of immigration (legal and illegal). If we did not have the immigration we have now, we would be experiencing population decline.
I will reference this book in another article on this subject, but I highly encourage the reader to check out the book “What to Expect when no one is expecting” by Jonathan Last.
The fertility statistics in this book are a real “inconvenient truth” to modern day feminists, and we face a much greater threat from dropping fertilities rates than any climate change, real or imagined. But I will have more to say about this subject in separate post dedicated to conflict between women’s rights and the survival of the human race.
But the second issue, and the one that this post is primarily dedicated to is the biological capacity of men for polygyny.
Even if practically speaking, we as men in western culture are for the most part living monogamous lives, it helps us to understand ourselves better, as well as our wives to understand to us better, when we all come to the realization that men are biologically built with the capacity for polygyny.
There are some men who have lower sex drives, and have less polygynous natures than other men, so that they would never desire to act on their capacity for polygyny. But the vast majority of men have a high sex drive, some higher than others, and definitely if our society allowed it would act on their natural polygynous desires and biological capacity of for polygyny.
This is why happily married men still routinely check out other women.
This is why it is not perverted for a 50 year old man to check out an 18 year old woman.
This is why men typically want to have sex multiple times a week, whereas many women would be happy with sex a few times a month.
Man’s capacity for polygyny is not only Biblical, it is also biological.
 Zanzig, T. (1999). Jesus of History, Christ of Faith. Terrace Heights, Winona: Saint Mary’s Press, Christian Brothers Publication. p. 89
 Weitzel, Eugene. J. (2010). I Want to Be a Husband and Father for Life and a Catholic Priest Forever. U.S.: Xilbris Corporation. p. 113
 Zvi Yehuda, “The New Babylonian Diaspora: The Rise and Fall of the Jewish Community in Iraq, 16th-20th C.E.”, p.97