Let's Flip the societal Clock

The age of consent is too high.  In European and North American cultures of the 20th and 21st centuries, marriages are contracted at age 20 or older. This is an absolutely ridiculous situation caused by the aberration of great wars. In Europe many men were destroyed by the two world wars. Surviving females with children posed a severe threat to the economies of their countries. Legislation was enacted to treat the symptom, single mothers, and not the disease, war. The most common laws restricted the marriage age in an upward fashion by raising the age of consent.  In North America, the Civil War resulted in the same kinds of laws being passed at even earlier dates.
Raising the marriage ages for both men and women did lead to an apparent reduction in single and unwed mothers. Unfortunately the reduction was short lived and most likely the result of an increasing balance of the sexes between and after these major conflicts. Still we are stuck with elevated legal marriage ages.
I said that this situation is ridiculous and here are my reasons.
Both males and females show almost no signs of infertility in their teenage years. Children born to parents, when both are teenagers, show few if any birth defects. But in both females and males there is a marked increase in infertility after the late teens. There have been many studies correlating the age of the parents with the number of birth defects. In every study, the number of birth defects rises significantly in each decade after the late teens. Men, in fact,  will contribute greater numbers of defective sperm and resultant birth defects in their children for each year they age past their teens. Their children will have lower intelligence, more mental illness, retardation and autism. A fertile old man is definitely a danger to society. Younger fathers and mothers are much more beneficial.
Children from the age of twelve show  responsible and mature behavior in societies that grant them adult legal rights. Societies that raise the age of adult legal status experience increased juvenal deliquency and antisocial behaviors in young adults and more problems with older adult social participation.  Many studies have been done that indicate the truth of these statements, although there  is no consensus of why.  It should be obvious that lowering the age of adult responsibility is beneficial to society.
Most education programs in the USA, I am not able to comment on European programs, demonstrate reduced participation by the students during the teenage years. All sorts of explanations are given for the high dropout rates and lowered achievement scores and each generation of teachers has been tasked with improving the curriculum. It is very likely that behaviorally and mentally capable students are negatively affected by being treated as irresponsible children. They simply stop relating to controlling teachers and a repressive environment.
With just these three acknowledgments, I suggest that we as a society give adult rights to twelve year olds with the right to marry. I further suggest that all adults over the age of 25 be required to use condoms and other birth control methods in every sexual encounter.